Introduction: Cook Up an Edible Magnifying Glass
Fear not, for I have a solution to all three problems! Even better, the solution is a a solution: a solution of sugar and water! We shall make our very own magnifying glass...out of hard candy!
How it works:
Light moves at different speeds through different materials. When it changes materials, depending on the angle it hit the material boundary , it changes direction. This is called refraction. A lens refracts light so that it makes things you're looking at seem bigger or smaller, depending on the type of lens.
Here's an analogy. Imagine that it's a really hot day, and you are at the pool, and you take a jump off the high dive. Air whistles past as you fall faster, faster...SMACK! Suddenly, you hit the water and slow waaaay down. You swim for the bottom as fast as you can, but you can never swim as fast as you were falling.
Light works the same way. When it is traveling through the air, it zips along like a six-year-old on a sugar rush. Suddenly, when it hits a pane of glass, it slows down as much as the same kid wading through water.
The angle that light hits glass is also important. It's like what happens if you dive off a diving board. If you dive straight in, you go straight down, and you go pretty quickly. However, if you dive at an angle, the surface of the water deflects you in a different direction. Don't believe me? Try belly-flopping. You'll be certain that the water is trying to deflect you right out of the pool.
Now that we've deflected off the subject enough- let's get back to lenses.
We're going to make a lens. All you need is some transparent substance, like glass or plastic, and a mold for the lens.
We shall make a plano-convex lens , which is a fancy Latin name for a lens with a flat bottom and a curved top. As for the transparent material, my transparent material of choice is inexpensive, easily accessible, easily polished, lightweight, low-melting-point, non-toxic, biodegradable, edible, and delicious.
In other words: hard candy.
We'll cook up a batch of hard candy, pour it in the mold, polish it, and voila! Instant magnifying glass.
- 1 3/4 cups Sugar
- 1 cup Water
- 1/2 cup Corn syrup (optional)
- 1/4 tsp Cream of Tartar (optional)
- flavoring (optional)
- 2 16oz. boxes of Corn Starch
- No-stick cooking spray
- smallish saucepan
- candy thermometer (somewhat optional)
- 1-inch deep cake pan (or bowl, or something suitably deep)
- candy-pouring crucible: either make one or use a glass measuring cup
- spherical object ( I used a ladle)
- A couple of children (optional, for the polishing step)
An air-conditioned home without much moisture in the air or a nice, clear, NOT humid day. (Ever wonder why hard candies get chewy over time? They're hygroscopic, which means they absorb water like mad. When candy absorbs water, it gets chewy and sticky, which is not something hard-candy manufacturers like, which is why they recommend making your candy on a nice, cool, clear day.)
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Step 1: Making the Mold
I like to set up the mold before making the candy, because making hard candy and pouring requires quick work and you don't want to be distracted trying to make your mold while you've got molten candy on your hands.
Take your one-inch deep pan and fill it full of corn starch. My particular pan is an eight-inch diameter pan, and it took two 16-oz boxes to fill it.
Level it off a bit so that it's full, but not overflowing.
Take your round object- in my case, my two-inch-in-diameter ladle- and press it deep into the corn starch. Like a meteor hitting the earth, you're going to displace a lot of starch, so it will sort of mound up on the sides before leaving a big crater. The bottom of the crater will probably be somewhat cracked or have imperfections. No problem- simply spin your spherical object in the hole to smooth it out. That's the advantage of making a round object mold: you don't run into big displacement problems like the instructable here .
Honestly, having a perfect mold does not matter in the slightest- from what I can tell, corn starch is not supposed to be used as a mold for things this big, because huge imperfections show up when you cast your candy if it's too large. On the other hand, it works in just fine in this specific case, because we get rid of those huge imperfections in the polishing stage later.
I was able to make four molds with my pan. This recipe has enough candy for six lenses, so you'll either want to get more corn starch or just do something else with the excess candy.
You'll probably have some candy left over at then end: I certainly did. It was enough for about two more lenses, although I didn't have enough starch to make six molds. Spray a cookie sheet with no-stick spray, and pour the excess onto the sheet, and let it harden. The cooking spray will keep your candy from sticking to the sheet like glue.
I also made an additional lens by spraying the inside of my ladle with no-stick spray and filling it with extra candy.
Step 2: Making the Candy
Let's get cooking.
Get your ingredients around. You need:
1 3/4 cups Sugar
1 cup Water
1/2 cup Corn syrup (optional)
1/4 teaspoon Cream of Tartar (optional)
For info on the science behind the ingredients and why nearly everything is optional, check out this lovely website .
This is the most dangerous part of the process. Liquid candy is charmingly called culinary napalm because it's hot and sticks to everything. Be careful. Wear an apron. Safety goggles would not go amiss. Remember, being a mad scientist means you destroy them all, not yourself.
I don't like to pour molten candy from a heavy pan directly into my mold, so I made myself a candy-pouring crucible like the one in this Instructable . I made my candy crucible out of an aluminum can, an awl, a three-foot piece of thin wire, and a wooden skewer. I like my design because when you pour candy into it, the molten candy will bubble up as the last bits of water vapor try to escape it. Since my hole is in the bottom of the crucible, there are not as many air bubbles in the stream of molten candy flowing out the bottom. If I had a pyrex glass measuring cup and poured from the top, i would get a lot more bubbles in my candy. However, if you do decide just to use a pyrex glass measuring cup, my experiments show that although it looks like you will have lots of annoying bubbles in your mold, most of them pop and go away as the candy sits and cools.
Got everything around? Good. Let's get started.
Mix the sugar, water, corn syrup, and cream of tartar in your saucepan. Stick it on your stove, and turn your stove up to high. I got out my wooden spoon and stirred my mixture to make this particular batch, but a professional cook recommends never stirring your mixture for better candy.
When the candy starts to boil, put in your thermometer. If you don't have a thermometer, you can use the cold water method to check how done your candy is. Make sure the bulb of the thermometer is in the candy. If it doesn't reach, you will have to tilt the pan and cover the bulb occasionally to check what the temperature of your candy is.
You will notice that at the very beginning, your candy solution looks like boiling water. Near the end, however, it looks like boiling oil: the candy is very thick and viscous, and it has turned slightly golden. It will take ten to fifteen minutes to get up to temperature. I do not recommend wandering away or setting a timer, because there is a very small difference between a nice, pale yellow hard candy and a burned, blackened, viscous mess.
While you're waiting, be sure that you have your mold nearby, as well as a cookie sheet or plate sprayed with no-stick for anything left over.
When your candy reaches about 290 degrees, turn off the stove. Hard candy is made at 300 degrees, and the pan will heat your candy up the additional few degrees. You do NOT want to go over 310 degrees, because that's when the candy starts to burn. I don't even like to go over 300 degrees. This is the point where you want to stir in a few drops of any flavoring you want.
Take your candy off the stove and pour it into your crucible. Let the bubbles settle for a about half a minute, and then, gently, very gently, start pouring the candy into the mold.
If your candy starts to set up while your pouring, and you're using a microwave-safe crucible to pour, go ahead and stick it in the microwave for fifteen to thirty seconds to loosen it up again, then continue pouring.
Now...we wait. Depending on how thick the candy is, it can take anywhere from ten minutes to an hour to fully harden. Because they're pretty thick, I give my lenses an hour to set on the counter.
After you're done, I recommend sticking everything- thermometer, crucible, pan, and all- in the sink and filled it with water. Sugar is water-soluble, so unless you burned it everything will dissolve away without any scrubbing.
Step 3: Polishing the Lenses
Your cool lenses have cooled- now it's time for the fun part!
Lift your lens from its bed of corn starch. You'll notice that there's a bunch of corn starch stuck to the bottom of it, and that the hard candy cracked your mold and formed a bunch of ridges on the bottom of your lens- it's impossible to see through it!
Never fear. It's time to polish it!
Make sure to hold your lens by the edges- otherwise you'll get fingerprints all over the lens, which will make it hard to see through, and you'd have to polish them off. Given HOW you're going to be polishing them, it's best to not get your dirty fingers all over the lens in the first place.
So, to polish, get out your high-precision mark 1 portable sugar polishing tool, also known as your tongue. Start licking.
The corn starch doesn't taste that great, but soon enough you'll get to the good stuff. This is where it pays off to flavor your candy. Plain hard candy is kind of dull.
This is also the part kids love, and, if you've kidnapped the neighborhood kids, you can always tell their parents that you weren't feeding them candy, they were helping you manufacture precision optics.
Tip for parents: if you've ever wondered how to get your kid to stop chewing on lollypops and to start licking them, make them into lenses!
How many licks does it take to polish a lens? Honestly, I don't know. I lost count after about 500.
Once you have your lens polished, with no bumps, scrapes, fingerprints or other surface-marring features, you lens is now ready to use as a magnifying glass.
DON"T put your lens directly on what you are trying to magnify. The lens will be sticky, especially after you got done polishing it. Instead, place a clear plastic sheet, like a sandwich baggie, on top of what you are trying to read, and put the lens on top of that.
Et Voila! instant magnification!
Step 4: Unanswered Questions
Your lens will be a clear yellow color, not completely white. I don't know if there is a hard candy recipe out there that lets you make transparent lenses without the yellow color, although I searched for days on google. I did make a transparent lens by stopping at the soft-crack stage, but the clear candy was taffy-like, and in a few minutes my lense slumped and did not hold its shape.
I don't know how long they will last. Conventional candy wisdom says that candy can last indefinitely in cool, clear conditions, but if you expose them to head and/or water, they will warp and dissolve away. Sugar is hygroscopic , which means that it likes to attract and absorb water. This is why, if you leave sugar out for too long, it will form a sticky film. In our case, that may actually be a good thing: the water softens the top layer of the lens, and it starts flowing a little bit. According to my experiment, this little bit is just enough to smooth out any remaining surface irregularities and bring your lens to a nice, high shine.
Of course, this high shine only lasts until your cat wanders by and leaves all of his cat hair stuck to your lens. After this happens, you can wash your lens off with water to get the hair and dirt off, but this will also dissolve the top layers of your lens, so you will have to spend about half an hour polishing it up again to remove the pits and flaws. Since by then the candy has attracted a lot of water, it is a bit flexible and will warp if you hold it in your hand long enough to actually recondition it. To recondition it without warping it, I recommend mounting it on some flat surface that you have sprayed with no-stick, such as a plate or a bowl.
To me, it seems like it took longer to recondition a lens than to make a new one- so take advantage of the fact that your lens is completely biodegradable and utterly harmless to the environment, and throw it out.
My Experiments show that if you take one of the lens outside and use them to focus the rays of the sun, if you shine it on your hand, it will get slightly warmer, but you cannot start a fire with it.
I am betting you can get sugar glass that is more bubble free by running it through a vacuum chamber to degas the sugar. Lolly-pop manufacturers make their hard candy in a vacuum , so it would be interesting to see if a homebrew vacuum chamber makes clearer glass.
Apparently, you can microwave hard candy . This may speed up the manufacturing process considerably. Also, college students, it means you can make these in your dorm room.
Now, fellow mad scientists! Go forth, armed with your magnifiers, and remember, they can take away your chemistry lab, but they can NEVER take away you your kitchen!
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