AI made the ice cubes by the directions I saw on another post, with the 1/2 cup corn syrup and 1/2 cup of sugar melted in microwave, that part all worked fine but I put them in the fridge to harden and when I took them out they just kinda melted. How to I get them to get hard and stay hard? Do they need to air dry? Will they end up melting when I put them on the cake? Any help is appreciated, I need the cake for this saturday. Thank you so much!

At first, my thought is that the sugar is undercooked.  Try it again and make sure it temps to at least 300, no more than 309 degree F.

If that does not work, reduce your amount of corn syrup and increase your sugar a tad.  Excessive amounts of corn syrup, glucose, cream of tartar will keep things more pliable for a longer time... not hard brittle like it should be.

last suggestion:  Just boil some sugar stovetop (hard crack stage- 300degrees, roughly) and pour into a mold of sorts that is not PVE, PVP, or PVC (i.e. tupperwares).

good luck!

I haven't seen your recipe for this, but I would advise to keep any type of cooked sugar out of the cooler :)  And also like zjones4 said, your sugar probably wasn't cooked to the proper temperature.  Hard to do in a microwave. 

The recipe I use for cast sugar is 500g sugar, 200g water, and 100g of glucose or corn syrup.  Make sure your pot is clean! Water and sugar in the pot, stir just until it boils, STOP STIRRING, add your glucose or corn syrup and just let it boil its way up to temp.  DO NOT STIR DURING THE COOKING PROCESS!!!!! Keep the sugar crystals off the sides of your pot by brushing it down with some water.  Once your sugar has reached the proper temp, pull it off the stove, ice bath it for like two seconds just to stop the cooking, and set it aside to cool a little bit before you  pour it into your molds. If you pour it too hot, it will crystallize, and bubbles will be trapped in it.  I recommend a digital thermometer if you have one, and if you want to add color, add it at 285 degrees, (again without stirring, it will have enough time to get incorporated). 

Since you are making ice cubes, you may want to see if you can get your hands on some isomalt.  Super easy to cook, and will stay crystal clear.  (Unless you get sidetracked and burn it lol!) <---done it, many times :) 

Also, I saw another user on here use gelatin for ice cubes... pretty crafty I thought.  

hth!

Also, if its humid where you are, your sugar will become tacky,  which is almost impossible to avoid.  If you go the sugar route, try not to make them too far in advance!  

AHere is my last suggestion. Let me preface that this technique needs a funnel and some clamps to hold things in place...otherwise there is a definite risk of getting burned. This is a techniques I use when making showpieces. I'll adapt it so it fits your needs and I'll leave it up to you if you feel this is the most practical thing to do or not. In your case it might not be, but I'll thorw the explanatin out there in case someone creative finds another use for this.

Oversimplified version Fill a vinyl tube with your cooked sugar (cane sugar or isomalt has no difference here). Cool and break off pieces the size you want using a chisel or knife.

More detailed version. Tightly clamp an end of a vinyl tube off and gently hold it with another clamp leaving the other end wide open. Stand the vinyl tubing upright like a pole and angle it a tiny bit. Place a funnel in the tube and cook your sugar/isomalt. When it is ready, let the pan sit on a few cubes of ice for a moment until the bubbles disappear and then pour into the vinyl tube. Let the sugar sit in the tube until it is completely hard. Cut away the tubing with a razor blade/boxcutter. Take a chisel or old knife and gently tap the blade with a hamer to break off the size pieces you want. A quick, light hit with the hammer is best. the knife is there to make the hammer more accurate.

This is a great technique when you want rods, curves, wavy lines, etc. This might not be the solution for you, but I give it just in case the right person is reading. as a note, the vinyl tubing is perfectly safe for pouring sugar into. It will not melt, but does get very hot, so I do not recommend holding it while pouring in the sugar.

A5 tips for preventing the sugar from getting tacky (due to humidity) 1. use isomalt. it resists absorbing humidity. it is not failsafe, but it helps significantly 2. keep in air tight container. 3. add silica packets/ limestone chunks (not powder) to the storage container 4. ccook the sugar slightly lower so it takes longer to get to temp. the extra time ensures all excess moisture amidst the sugar molecules are gone. 5. coat with acrylic. if using around food this is not recommended. Apply using a brush, or better yet, an airbrush

To retard stickiness you can also paint on shellac or confectioners glaze/ varnish but it does give a slightly misty look sometimes.

isomalt is what i used tryed the sugar  way and where yellow