Cook Up an Edible Magnifying Glass

Hello, fellow mad scientists!  Are you sad that the state police blew up your high-precision optics lab with attached glassworks? Did the Feds storm your volcano fortress after you released a plague of self-replicating Tribbles upon the House of Representatives?  Are your blood sugar levels dipping dangerously below the recommended levels for unbalanced geniuses?  

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.


Supplies: 

Food supplies:

• 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

Cooking Supplies:

• 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

Other Supplies

• 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.) 


I am indebted to the following instructables: 
http://www.instructables.com/id/Sugar-Glass/
http://www.instructables.com/id/Corn-Starch-Candy-Molds/

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.

Comments

[sunshiine]

I love this! Thanks for sharing!

[jessyratfink]

These look like a lot of fun! I can imagine having a silly Sherlock Holmes party with these.

[Tararoys]

Oooh! Now there's an idea.

[janw]

Looks like great fun! Nice instructable too. It would be nice if you could give it the typical detective spyglass look by giving it the typical frame.

[Tararoys]

That would require a convex lens, where both sides are curved. I haven't quite figured out how to easily mold a convex lens out of kitchen supplies, but you can expect an edit- or a brand new instructable- when I do.

[rimar2000]

No, Tararoys, you don't need a biconvex lens to do one of these magnifying glasses. Good Instructable!

Do you know if there is a way to clearer a bit more the sugar?

[Tararoys]

One of my next experiments is going to be degassing the sugar, like you do with silicon molds. This involves sticking the molten sugar in a vacuum chamber for a little bit, to get all of the bubbles out. I'm still building my vacuum pump, but once that experiment is done I'll definitely either update the instructable or make a new one.

I don't know a way to make the sugar less yellow and still be hard enough for a lens. I did make a clear sugar lens that wasn't yellow, but the lens was as flexible as taffy, which meant that I had to be really careful about how I touched it or I would destroy it's lens-like properties. It doesn't last as long as these yellow lenses, which so far have lasted 3-5 days in high humidity.