Grasshopper Tracks

Fireworks - Lessons in History, Science, Math and Art

7/3/2016

With the 4th of July/Independence Day in the United States approaching (and now upon us), I decided to create some learning activities for my kids that center on fireworks. The topic allows for incorporating several disciplines, including history, science, math and art. I've included links to resources and to activity options that I either did or am planning to do.

Fireworks Safety
Fireworks safety is an important topic to cover with kids, and a couple good resources for some firework safety tips are:

The History of Fireworks
China is generally credited with the invention of fireworks. For discussing the history of fireworks with my kids, I found these links as useful resources:

Science and Fireworks
It is difficult to do many hands-on science projects involving fireworks with young kids because, well, explosives and young children are not a good mix. Nevertheless, I came up with or happened upon a couple activities that were safe for kids (with adequate adult supervision).

Dissect a firework to see it's components, and explain how it works at a high level.
- I chose to use an inexpensive daytime aerial parachute firework, and purchased two - one to cut into, and the other to set off so that we could see the firework in action. I found a page with a good diagram of an aerial parachute firework that helped us identify the component parts in our firework and explain how it worked. (The site, Powder Keg Fireworks, has good diagrams and explanations of several other fireworks as well.)

Observe the making of a homemade smoke bomb, followed by a very basic discussion of what is occurring. The smoke bomb we observed was made from potassium nitrate (a.k.a. saltpeter) and sucrose (a.k.a. table sugar). This requires safety precautions, and should be done by an adult or responsible older kid only.

Heating the potassium nitrate and sucrose.

Pouring the caramelized mixture into a mold.

Lighting a piece of the smoke bomb.

Make "fireworks in a jar," which is really a simple experiment on liquid density using oil, water and food coloring. This post on Active Wild can help with explaining density to kids as well.

Approximately 16 drops of food coloring in 4 tablespoons of oil, mixed gently (avoid mixing too much if multiple colors are desired).

Slowly pouring oil/food coloring mix into a jar of warm water. The food coloring (water-based) is more dense than the oil so "falls" into the water, creating a mini-explosion of color in the water.

Watch this video from Science Kids which shows some of the chemistry behind the color of fireworks.
Do this experiment from Science Buddies to see how a couple different metal salts, when burned, create some of the different colors seen in fireworks. Table salt is one of the metal salts used in this experiment, so is very accessible.

Math and Fireworks

Introduce the math terms parabola and trajectory, and explain that math allows people to safely plan fireworks shows...this is one way to plant a seed about how useful math is and how fun it can be. (I like to use either our little hand-held whiteboards or our large 6-foot whiteboard to draw and help explain concepts like this, preferably with the kids copying what I am drawing.) I used this post on math and fireworks from Math for Grownups as the basis and background for this activity. I also like the author's suggestion of having a child toss a tennis ball up at different angles to help understand the concepts of a parabola and trajectory.
Use the purchasing of fireworks as a math and finance lesson by giving a child a certain amount of money to spend , and help them figure out what they can and cannot afford to buy (using a variety of dollars and coins can help a child practice money identification and value, if they are ready for that). This involves addition, subtraction, greater than/less than, money concepts and so on. Examples: "If you have $5, how many $2 firework cones can you buy?" or "If you have $5, do you have enough to buy 3 packs of snappers at $0.50 each and a bag of smoke bombs for $1? How much money would you have left over?" Similarly, math skills can be practiced when enjoying the fireworks too: "You bought 6 smoke bombs, and you've set off 2. How many do you have left? If you share them equally with your sibling, how many can each of you have?"

Firework Art

Make toilet paper tube firework art. There are several examples of this online, but we referred to this post on Crafty Morning.

Use glitter and glue to make firework art, as shown in this Kids Activities Blog post. I like the way this art looks, but haven't done it with my kids, and haven't decided if I will since I have such a dread of glitter in the house because I will continue to find pieces of glitter for months afterwards.
Any online search for fireworks art or fireworks crafts ideas will likely produce many other great options, as evidenced by the extensive list on this Pinterest site.

Other Resources:

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The American Revolution - Play and Reading for Kids

6/30/2016

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As the Fourth of July nears, I have been reading the kids several books related to the American Revolution. I want them to understand what the holiday means, to be introduced to the history of the United States of America, and to understand a bit about what it means to fight for what one believes in and for what one believe their rights to be. In conjunction with reading, I've helped the kids create play inspired by the American Revolution. Hopefully, this helps them to better imagine scenarios and to solidify some of what they are learning. Our reading and play activities are outlined below.

Kids' Play Related to The American Revolution

I found a relatively inexpensive American Revolutionary War toy soldier set at Hobby Lobby for just $10, which only cost me $6 with their weekly 40% off coupon (it has Colonial soldiers in blue, British soldiers in red, and German Hessians in black, as well as General George Washington and his white horse, General Charles Cornwallis, and French General Marquis De Lafeyette). To create more figures, I bought some round doll pins with flat ends; cut red, blue, white, and brown strips from felt rectangles; notched the strips in the center; pushed the strips over the doll pin "heads" to create clothing; and tied the felt "clothing" down with a small piece of crochet thread. These figures can be made to represent women of the time by making the felt strip a little longer to suggest a dress. For other projects, I've painted faces and hair on the doll pins with acrylic paint, and the same could be done here - however, I wanted to leave the option to use the doll pins for other projects once our Revolutionary War play has run its course. We've incorporated craft picket fences, miniature wooden pickle barrels, popsicle sticks (for whatever the mind can imagine), Lego ships, rocks, and a myriad of other toys and objects into our play. My kids have pretended to have a Boston Tea Party, fight the Battle of Bunker Hill, and re-enact other key events in the American Revolution, all with a great deal of liberty in the re-enactment, just as child's play is wont to do (who knew that a truck carried the soldiers to Breed's Hill and that there were Lego pirate ships sailing right next to the hill pulling barrels of ammunition through the water?). Ultimately, I want them to have fun with the topic and get an introduction, and I think we've achieved that.

Kids' Books Related to The American Revolution

There can be many accounts of history, with the story differing depending on who is doing the telling. This in itself can be a lesson on the importance of listening to different sides but being willing to question and seek the most accurate answers before forming one's own opinion - to not just consider those accounts that feel good or that reinforce what we want to believe to be true or have always accepted to be true. To be fair, the goal of some texts or verse is not so much historical accuracy, as it is to incite some sense of bravery or patriotism (example: The Midnight Ride of Paul Revere by Henry Wadsworth Longfellow), and I think such writing has its place. However, I want to point this out to my kids, in the hope that they may grow to be discerning readers with an understanding of context. This is certainly not always easy to do, particularly when, in my opinion, historiography sometimes tends to be one-sided and neglectful of topics that don't best serve the majority or those with the most power. Historical accounts that are presented as strictly factual accounts (such as textbooks) may have an underlying agenda, such as instilling patriotism or casting historical figures as absolute embodiments of the particular values we want to transmit to our children...not to mention that the waters can be further muddied when there is legitimate disagreement over factual accuracy regarding what truly occurred in the distant past. In my selected readings for the kids, I tried to also find some texts that highlighted groups whose achievements are often overlooked in the retelling of history. In this case, I specifically sought texts that described the role of women, African Americans and Native Americans in the American Revolution. I had some luck with the first, very limited results for the second (and geared toward kids older than mine), and although I searched for books on the role of and impact on Native Americans in the American Revolution and found some texts for adult-level reading, I did not come across any for children. To me, this is indicative of the need for more inclusivity in children's literature. Below are several titles that we have checked out from our library and have been reading.

Joining the Boston Tea Party (The Time-Traveling Twins)
by Diane Stanley, illustrated by Holly Berry
Recommended for ages 5-10
This is a fun approach to learning about the Boston Tea Party, as it follows a pair of time-traveling twins as they go back in time to visit their ancestors.

The Boston Tea Party
by Russell Freedman, illustrated by Peter Malone
Recommended for ages 8-11
This is written and illustrated in the style of a storybook, but is a somewhat lengthy, factual retelling of the Boston Tea Party.

You Wouldn't Want to Be at the Boston Tea Party!: Wharf Water Tea You'd Rather Not Drink
by Peter Cook, illustrated by David Antram
Recommended for ages 8-10
This is a humorous, fun-loving, and sometimes silly approach to history. There are several books in this series, which can make learning about history attractive for many kids.

Let It Begin Here! Lexington & Concord: First Battles of the American Revolution
by Dennis Brindell Fradin, illustrated by Larry Day
Recommended for ages 6-10
This book is a nice way to introduce younger children to the first battles of the American Revolution.

Let It Begin Here! April 19, 1775: The Day the American Revolution Began
by Don Brown
Recommended for ages 7-10
This is similar to the above title, but is a longer story and is more appropriate for kids who can maintain attention levels a little longer.

The Declaration of Independence (True Books: American History)
by Elaine Landau
Recommended for ages 7-9
This is an informational text, not a storybook, so may not be as appealing to some children. My kids tend to do well with these types of books, and enjoy the drawings, paintings and photographs.

George vs. George: The American Revolution as seen from Both Sides
by Rosalyn Schanzer
Recommended for ages 9-12
This book is helpful in encouraging kids to try to see the perspective from the other side - or at least gain greater understanding of where they are coming from - regardless of whether you end up agreeing with it or not.

DK Eyewitness Books: American Revolution
by Stuart Murray
Recommended for ages 8-12
While this book is geared towards older kids, I find that it is still a nice way to show pictures of people and artifacts associated with the American Revolution. My kids find the pictures interesting, and we skip around the book reading tidbits of information as they see fit. The DK Eyewitness series is produced in association with The Smithsonian Institution and is reminiscent of a visit to a museum.

Independent Dames: What You Never Knew About the Women and Girls of the American Revolution
by Laurie Halse Anderson, illustrated by Matt Faulkner
Recommended for ages 6-10
This is a great book for exposing kids to the role women played in the American Revolution and introducing them to some of the more notable female figures of that time. The book provides quick snippets of information about several women, as well as a timeline of events during the Revolution.

Founding Mothers: Remembering the Ladies
by Cokie Roberts, illustrated by Diane Good
Recommended for ages 7-12
This book is more wordy and detailed than the above text, so may be better suited for older children, but is still a great way to quickly learn about the ladies of the American Revolution. I am able to skim over the text and provide my kids with a synopsis, but this is a book I plan to bring out again when they are older. For adult-level reading, I recommend Cokie Roberts book Founding Mothers: The Women Who Raised Our Nation.

America's Black Founders: Revolutionary Heroes & Early Leaders with 21 Activities
by Nancy I. Sanders
Recommended for ages 9-12
This book is really too advanced for the age of my children - it is primarily wordy text with some black and white pictures. However, there are some good suggestions for activities, nice synopses of several notable African Americans of the 1700's and early 1800's, and some good background on the role of and impact on African Americans around the time of the American Revolution. The information in the book can be used for general discussion with younger children.

Sybil's Night Ride
by Karen B. Winnick
Recommended for ages 5-7
This is an enjoyable storybook relating the tale of Sybil Ludington, a 16-year old girl who rode through the night to warn her father's, Colonel Ludington's, militiamen of an oncoming British attack. Her nighttime ride was more than twice the distance of Paul Revere's famous ride.

Katie's Trunk
by Ann Turner, illustrated by Ronald Himler
Recommended for ages 5-8
This is a good storybook for younger children, and I appreciated how it humanized the people involved in the Revolution, both those loyal to Britain and those rebelling against Britain. The story is based on an actual incident with the author's ancestors, and is centered around a loyalist/Tory family. The book provided an opportunity to discuss with my kids how, regardless of how much our beliefs and ideology might differ from those around us - including our family and neighbors - we should not let that make us forget our and others' humanity.

They Called Her Molly Pitcher
by Anne Rockwell, illustrated by Cynthia von Buhler
Recommended for ages 3-7
Many experts now believe Molly Pitcher was a mythical figure who was grounded in fact, a composite of camp followers. Though the author's note in this book indicates that Molly was a real person named Mary Hays McCauly, other texts insist that there is evidence to the contrary. Regardless, this is still an enjoyable story and one of the enduring legends of the American Revolution.

George Did It
by Suzanne Tripp Jurmain, illustrated by Larry Day
Recommended for ages 5-9
This book does a nice job of using light-hearted prose to create a more human portrait of George Washington, revealing his reluctance and nervousness about assuming the presidency.

Thomas Jefferson: Third President (Getting to Know the U.S. Presidents)
by Mike Veneza
Recommended for ages 6-9
As the title and series suggest, this is an informative book and not a storybook. The text is written in language understandable to younger children, so although a bit dry, some children may find the historical pictures and cartoon drawings enough to keep it interesting.

Benjamin Franklin from A to Z
by Laura Crawford, illustrated by Judith Hierstein
Recommended for ages 7-10
Though not as engaging as a storybook, this book does provide some interesting snippets of facts about Ben Franklin.

A Picture Book of Paul Revere
by David A. Adler, illustrated by John & Alexandra Wallner
Recommended for ages 6-9
Like David Adler's other picture books highlighting historical figures, the story is factual, but written well for younger children, and the illustrations maintain interest.

Those Rebels, John & Tom
by Barbara Kerley, illusttrated by Edwin Fotheringham
Recommended for ages 7-10
This book, though a long read for young children, has fun illustrations and enjoyable writing. It juxtaposes John Adams and Thomas Jefferson, two very different many who often disagreed but together "helped launch a new nation."

DVD: Liberty's Kids - The Complete Series
Rated G
This is not a book, but rather a DVD series of 40 episodes. The series follows Benjamin Franklin's fictional teenage reporters, a young colonist named James and a young Englishwoman named Sarah, through the many events leading up to and through the American Revolution. My kids love this series, and though we are still in the earlier episodes (it will take us awhile to get through these since I limit screen time), they are asking me each day to watch more. I tend to prefer books to movies, but this series is a fun and easy way to expose kids to the events of the American Revolution.

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Strawberry Time

5/15/2016

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Strawberry season is upon us. Although store-bought strawberries are available nearly year round now, this is the time when some pick-your-own farms are open. Picking berries is one of my favorite late spring/early summer outings with the kids. I think it is a great opportunity to get them a little closer to the starting point of one of their food sources and to appreciate the work that goes into bringing food to market. Plus, it is just plain fun outdoor family time.

We typically pick several pounds of strawberries and freeze most of them - wash, hull, place on cookie sheets lined with parchment paper, flash freeze, then put in a bag and store in our deep freezer. However, we do save some fresh strawberries for making a couple special treats. As I was trying to decide what to make this year, I found myself contemplating coconut and lemon flavors in conjunction with the strawberries. I am not someone who generally invents my own recipes, so I began brainstorming about how I would like to combine these flavors and then searched online for recipes that might align with my ideas. I came up with two dishes that my husband and I have made over the past couple days - Strawberry Dutch Baby with Coconut Rum Strawberry Syrup and Coconut Lemon Scones with Strawberry Whipped Cream and Macerated Strawberries. Both of these have been successes, and I definitely want to make these again.

Strawberry Dutch Baby with Coconut Rum Syrup

We had coconut rum in our cupboard, so I began searching for strawberry rum sauce recipes, planning to just use coconut rum instead. I don't enjoy drinking hard liquor, but I do like the flavor that it provides in cooking and baking. I came across a Strawberry Dutch Baby with Fresh Strawberry Rum Syrup recipe on The Cooking Photographer website. This sounded perfect to me - Dutch baby pancakes are easy to make and yummy - so we made the recipe as written with only one adaptation - using coconut rum in place of regular rum. We loved it...especially the rum syrup! The syrup is versatile and I can imagine using it on many things. We have already stirred it into our plain homemade yogurt for a tasty snack or dessert.

Coconut Lemon Scones with Strawberry Whipped Cream

I wanted to try a twist on the classic strawberry shortcake that included coconuts and lemons. After doing some searching, I came upon a Coconut Lemon Scones Recipe at one of my favorite food blogs, Two Peas & Their Pod. Given that I have liked so many of the recipes from this site, I was confident I would enjoy this scone recipe as well. The kids enjoyed watching me make the scones, and cutting the round of dough into eight pieces was a nice opportunity to discuss fractions with them. (I find cooking, in general, to be a great time to incorporate math lessons). My plan was to top the scones with plain whipped cream and macerated strawberries (i.e. sliced strawberries sprinkled with a bit of sugar to draw the liquid out), but Hopper 1 said he wanted strawberry whipped cream. Since I like for the kids to feel involved in cooking (hoping that they will do more of it for me as the get older), I obliged. We simply pureed fresh strawberries and folded a bit into the homemade whipped cream. This Alton Brown whipped cream recipe is pretty similar how we make our own whipped cream. The resulting scones with strawberry whipped cream and macerated strawberries were a very nice twist on strawberry shortcake, and really satisfied my craving for a coconut/lemon/strawberry combination. (For a little more coconut flavor, my husband and I added a splash of coconut rum to the strawberries on the top of our servings...mmmmm, that coconut rum could become a dangerous thing.)

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Science for Young Kids: Anatomy & Physiology - Blood

5/15/2016

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The fifth lesson that I covered in an A&P unit for younger children dealt with blood. Previous lessons centered on the skeletal system, the central nervous system, the respiratory system, and the cardiovascular system. Our lesson on blood tied in well with the latter, and provided some review.

Activities:

Read the book A Drop of Blood by Paul Showers, illustrated by Edward Miller. This book was recommended for an older age group than what my children are, but with several breaks for discussion and explanation, they remained engaged.
Reviewed the pages on the heart, blood and circulation in our book Eye Wonder: Human Body. The book has some very nice microscopic photographs of cells, the interior of the heart, the inside view of an artery, capillary networks and so on.
Completed a short project to demonstrate how bruises are injuries where blood vessels break and blood leaks out and can be seen where it collects beneath the skin. I came upon this project on the site Our Time to Learn in a post about injuries. We adapted the project somewhat to use materials we had on hand: paper towels, straws, food coloring and water. I traced the kids' hands and forearms onto paper towels, placing a second paper towel beneath each one. Next, I cut our straws into shorter pieces and added red and blue food coloring to water to create a blood-colored liquid. I carefully put the liquid into the straws and laid each straw piece between the prepared layers of paper towels. The kids then hit the straws, causing the liquid to shoot out and create what looks like a bruise on the hand and arm. We had a few trials - getting enough liquid in the straws and getting it to stay there until being hit was a bit tricky. But overall, the kids understood the concept of how a bruise is formed.

Made a model of blood, based on the post "What's Inside a Drop of Blood" by Creekside Learning. For this model, we again went with what we had on hand, as well as adding an element to represent fibrin. As we added blood components, I also had the kids draw a diagram of the components onto their mini whiteboards, using differing colors of dry erase markers for each component. Our steps used in creating this model are shown in the following slideshow.
- Items used: corn syrup, dry lentils, red cinnamon candies, white poker chips, white string, bowl, mini whiteboard with various colored markers

Discussion points:

Blood has four main components - plasma, red blood cells, white blood cells, and platelets.
Plasma makes up more than half of our blood (55%), and is a clear, light yellow liquid which transports the other components as well as many other substances that our bodies needs.
Red blood cells (RBC's) make up a large portion of our blood (45%) and carry oxygen to and carbon dioxide away from our cells. The RBC's are small and are red-colored due to having hemoglobin, which is red-colored and contains iron.
White blood cells (WBC's) make up a very small portion or our blood (<1%) but are very important in fighting off germs, bacteria and viruses. When people are sick, their bodies release more WBC's. The WBC's are larger than RBC's, and there are several different types.
Platelets are small, sticky cells that help to form clots when there is an injury that causes bleeding. They also comprise a small portion of our blood (<1%). Platelets are assisted in their clot-forming job by fibrin, a thread-like substance that helps the clot stay together.
Blood also carries other things that our bodies need to function properly - like nutrients, proteins, and hormones - as well as wastes that our bodies need to dispose of.
Bruises, also called contusions, occur when small blood vessels break due to being bumped. Blood escapes from the blood vessel and collects under the skin, forming the coloration of a bruise. A bruise will change colors as it heals.
If a person is injured and loses too much blood, they can die. However, when people lose blood from injuries or operations, some of their blood can be replaced by blood donated by other people. This is how someone can help to save a life by donating their blood (though they have to be a healthy, old enough and big enough to donate). Blood donation involves taking blood from one person using a needle and tube and putting that blood into another person, after the blood has been checked and received special treatments. When a person donates blood only a small amount is taken, so the donor will still be okay.
Since blood carries so many substances needed and released by our bodies, it can indicate a lot about a person's health. Sometimes, a doctor may order a blood test so that a person's blood can be checked to ensure they are healthy. During a blood test, a needle is inserted in to a blood vessel to withdraw a very small amount of blood. It might sound scary, but it doesn't hurt very much, doesn't last very long and is often necessary to make sure a person is healthy.

Vocabulary words:

Plasma, red blood cells, white blood cells, platelets, fibrin, contusion, blood donation, blood test

Additional activities (which we didn't do this time, but I'd like to do sometime in the future):

Watch a video about blood donation, such as this one by Florida's Blood Centers.
Explain the different blood types (A, B, AB, O).

Resources:

KidsHealth provides an explanation of blood, along with a video about what is involved when getting a blood test.
The Women and Children's Health Network in South Australia has a Child and Youth Health page that provides good kid-friendly information about blood.
Easy Science for Kids has a succinct explanation of blood and a drawing indicating what percent of blood is comprised by each component.

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Homemade Yogurt

5/11/2016

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A few years ago, my husband and I began making our own yogurt as a means of cutting costs. What we didn't expect was that it would ruin the appeal of nearly all other store-bought yogurt. Not only is our yogurt less expensive, but we are amazed at how much better it tastes than what we can buy in a store. It took me awhile before I tried making my own yogurt because I thought it would be complicated, difficult or time-consuming. None of this has been accurate, as the process is really very simple, and actual hands-on time is minimal. I am able to start the process when I wake in the morning and have Greek-style yogurt by the following morning. There are various factors that can alter the taste of homemade yogurt, and we had (and occasionally still have) some batches that are not as tasty. However, after playing around with yogurt starters, methods of heating, culture time and more, we've come up with a process that usually results in a yogurt flavor, consistency and degree of tartness that we like. We prefer a Greek-style yogurt, but this process also works for regular, more fluid yogurt - we simply strain regular yogurt to get to the thicker Greek-style.

The basic idea of making yogurt is very simple: 1) Heat milk to a high enough temperature to kill off any "bad" bacteria (165° - 180°F); 2) Cool the milk down to a temperature that won't kill off "good" bacteria from the starter culture (110° - 120°F); 3) Stir in the starter, which is 2-3 tablespoons of plain yogurt with live active cultures per gallon of milk used; 4) Let the milk/starter mixture sit in a warm area (90° - 110°F) for several hours (4-10 hours generally) until thickened to a yogurt consistency; 5) Optional - if desiring Greek-style yogurt, strain the yogurt for several hours to extract some of the whey.

That is the process in a nutshell. But if you want more detail and tips on the yogurt-making process, specifically the process that we use, keep reading.

How to Make Greek-Style Yogurt

Only 2 ingredients are necessary:

Milk (for this process, we use cow's milk; the process will be similar for using milk from other animals, but differ somewhat for alternative plant-based milks)
Plain yogurt with live active cultures (the label on a carton of plain yogurt should indicate if it has live active cultures)

Some people also use gelatin or pectin as a thickener, but we do not.

Step 1: Heat milk to 165° - 180°F
This step destroys the "bad" bacteria in the milk.

The amount of milk to heat depends on how much yogurt is desired. More milk is required to make the same volume of Greek-style yogurt as regular yogurt since a large volume of whey is strained off when making Greek-style yogurt. We use a 6.5 quart slow cooker to heat our milk, so we purchase 2 gallons of milk to make a full batch, with some milk left over for other uses.
Yogurt can be made from a variety of animal milks, but so far we have only used pasteurized and homogenized cow's milk. Ultra-high temperature (UHT) pasteurized milk should be avoided, as the proteins needed to form yogurt may have been broken down. Either whole, 2%, 1%, or skim milk may be used, though milk with a higher fat percentage will produce thicker and creamier yogurt. (I personally don't notice a significant difference, and we usually use 2% or 1% milk.)
Our method for heating the milk is to pour it into our 6.5 quart slow cooker and heat on the high setting for 4 hours. Our slow cooker has consistently heated the milk to the required temperature range with this method, so I no longer even check the temperature. Once the slow cooker has finished heating, it can warm until we are available to move on to the next step, but I have noticed that a longer cook/warm time results in a more yellow-tinted yogurt with a taste variation that I don't care for as well.
We initially heated our milk in a stock pot on the stove top, but this required occasional stirring and monitoring to ensure the milk didn't scald or burn on the bottom (the latter lent a burnt taste to the yogurt that was not pleasant). The slow cooker method is more consistent, and we can just turn it on and leave it.

Step 2: Cool milk to 110° - 120°F
This step brings the milk to a temperature where the live cultures that are to be introduced can survive and thrive.

We use an ice bath to quickly bring the milk down to the desired temperature, with this entire step taking less than 10 minutes. We pour the milk into a stock pot (carefully, because it is very hot); dump ice into our sink and add cold water; then place the stock pot in the ice bath, insert a thermometer and spin/stir the milk until we get to 110°F.
The milk can be allowed to cool on its own, but this usually takes several hours, which might be fine if one is not able to move on to the next step as soon as the milk is finished heating, but might not be ideal if one wants to have yogurt available within a shorter time frame. I find that the slow-cool method can result in a more yellowish yogurt and a different flavor - at least I can detect a flavor difference.

Step 3: Add the yogurt starter culture (plain yogurt with live active cultures) to the cooled milk
This step inoculates the milk with the "good" bacteria that will culture the milk and thicken it into yogurt.

Add 2-3 tablespoons of plain yogurt with live active cultures (the yogurt starter) per gallon of milk used.
To add the yogurt starter, remove about 1-2 cups of the warm milk, gently whisk the starter into it, then add the milk/starter mix back to the rest of the milk and stir it in.
Plain yogurt saved from a previous batch of homemade yogurt can be used as the starter culture. Based on our yogurt-making trials, we hypothesize that continued use of this results in a yogurt that is more tart than what we prefer, so we usually buy a new container of yogurt at the store to use as our starter. However, now that we have found a process that controls enough variables to rather consistently produce a nice, mild yogurt for us, I plan to try this again to see if I still find tartness to be a factor.
Though our hypotheses are not entirely scientific, we think that the brand of starter yogurt culture we use makes a difference in the final flavor of our yogurt. The plain yogurt brand we prefer is Fage Greek-style yogurt. Among the store bought yogurt we have tried, this one comes the closest in taste to our homemade yogurt (though I think ours is still better).
Optional: Some people will add in a thickening agent at this point, such as gelatin or pectin. However, if you plan to make Greek-style yogurt by straining, as we do, this is not necessary.

Step 4: Allow the milk and starter culture mixture to rest in a warm area at 90° - 110°F for several hours until thickened
This step provides the right environment for the live culture bacteria to culture the milk and thicken it into yogurt.

The longer the yogurt cultures, the more tart and thick it will be, so the amount of time to culture is somewhat based on personal preference. Some people have a consistency and flavor they like after 4 hours, but I have found that I prefer the yogurt to culture for about 8-10 hours.
We have discovered that the most convenient way for us to keep the yogurt at a warm enough temperature for several hours is to pour our milk/starter mixture back into our slow cooker crock, cover it with the lid and a hand towel, and put it in our over-the-stove microwave with the stove light on the bottom of the microwave turned on. It is a bit of a pain to remove the crock whenever we need to use the microwave, but it does a good job of creating a warm, insulated environment.
For those who are concerned about milk/yogurt being at warmer-than-room-temperature for hours and possibly leading to foodborne illness, it may be reassuring to know that we have never had an issue. The heating of the milk in step 1 killed off all "bad" bacteria, and as long as bacteria aren't re-introduced by contaminated utensils, equipment, et cetera in other steps, this shouldn't be a problem.
The timeframe on this is somewhat forgiving, as we have occasionally forgotten about the yogurt, leaving it to warm all day and through the night. There have been no negative consequences other than flavor differences that might not be our preference but yet still result in good yogurt.

Following this step, if regular yogurt is the desired result, the process is complete. The yogurt can be placed in other containers and refrigerated. However, for Greek-style yogurt, there is one more step....

Step 5: For Greek-style yogurt, strain the cultured yogurt until the desired consistency is achieved
This step removes liquid acid whey (distinguished from sweet whey used in protein powders) from the yogurt.

Our process for straining out some of the acid whey is to line a large colander with coffee filters, place it over our stock pot, pour the yogurt from step 4 into the colander, cover with a lid, and place in our backup refrigerator in our garage for several hours (typically overnight). To prevent the coffee filters from moving as we pour the yogurt into the colander, we first use a spray bottle to spritz water on them so that they will adhere to the walls of the colander. Some people prefer to use cheesecloth for straining, but we find our colander and coffee filter method to be less expensive than buying cheesecloth.
We usually strain for 8-12 hours, and often the yogurt left in the colander is thicker and more dry than we would like. However, the timeframe on this step is also forgiving - we can easily remedy too thick/too dry yogurt by putting the yogurt into whatever container we plan to store it in, pouring some whey back onto the yogurt and then mixing it in well with a whisk or our electric hand mixer. The mixing also results in a more smooth, even consistency throughout the yogurt.
The acid whey can be saved for other uses (see below) or discarded (please consider the high acid content of acid whey when choosing where to discard - it is harmful to waterways in large quantities).

Finally, enjoy!

Now the yogurt is ready to be enjoyed. I typically prefer to eat my homemade yogurt plain. I cannot say the same about most store bought yogurt I've tried, but I find my homemade yogurt to be so tasty that plain is fine for me. When I or my kids do want flavoring (and the kids generally do), some of my favorite ways to add flavor or dress it up are:

Honey
Mashed banana (this does oxidize and turn the yogurt a brownish color if not eaten right away)
Nuts (sliced or slivered almonds, chopped walnuts or pecans, toasted nuts...they are all good in my book)
Fresh or frozen fruit (blueberries, strawberries, peaches, et cetera)
Lemon curd - a nice dollop of homemade lemon curd stirred into our yogurt is as good as a bowl of ice cream, in my opinion.
Cranberry relish - we started doing this around Thanksgiving, when we had leftover cranberry relish, and it quickly became a favorite; the creamy yogurt softens the tartness of the relish and the combination is really wonderful!
Rhubarb sauce - mentioned in a previous post discussing farmer's market favorites
Mashed sweet potato - stirring in the sweet potato creates more of a savory yogurt, especially if you add a few spices, but it is really yummy; it is reminiscent of sour cream on a sweet potato. I first tried this when I made the combination as a first food for Hopper 3, an infant at the time. I took a bite, and decided to make some for myself.
A combination of the above.

Other uses for plain yogurt:

Can be used in place of sour cream in many recipes, such as toppings for tacos (I personally still prefer sour cream over yogurt on my tacos...yogurt doesn't have quite the same taste) or in baked goods that call for sour cream (e.g. some cake or muffin recipes use sour cream to make a more moist product).
Add to soups for creaminess. I like to put a dollop in my tomato soup and stir it in to create an instant creamy tomato soup.
As a base for homemade salad dressings or vegetable dips - just add some salt and spices and some milk to thin, if needed.

Using Leftover Acid Whey

Making Greek-style yogurt produces quite a bit of leftover acid whey. This whey is a waste product which is harmful to waterways, making the disposal of it problematic for companies that produce large quantities of Greek style yogurt. Many companies are becoming innovative with ways to reuse acid whey, and there are several ways in which the whey can be reused at home too. An internet search for how to use whey from homemade yogurt will likely return several results. Frankly, we have not tried many uses ourselves, so I'm passing along information more than speaking from experience. As a side note, I've heard that acid whey can keep in the refrigerator for months, but I have not found that to be the case for us - black growth has appeared around the rim of our container after several weeks.

A few possible alternatives to discarding acid whey:

Replace the water or milk in most baked goods with an equal amount of whey – just add 1/2 teaspoon of baking soda per 1 cup of whey to help with leavening. We have tried this with some of our baked goods, such as waffles or muffins, and they have turned out well.
Add to smoothies
Use to make ricotta cheese
Use a diluted mixture to water plants
Feed to pets
Add to a compost pile

For more reading on issues with mass disposal of acid whey and on useful solutions for this food production byproduct, here are a few resources:

If you decide to try making your own homemade yogurt, it may take some trial and error until you get to the flavor and consistency that you like. Hopefully you'll stick with and will enjoy your yogurt as much as our family enjoys ours!

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