Other than gelatin what makes gumthe bears chewy

As you mentioned it is all about how the crystals form.

Some of the factors off the top of my head:

• How saturated is the solution - The more sugar packed into the syrup the more easily it will crystallize.
• How quickly it cools - The slower the bigger the crystals
• Interference - Do you have a starch or other sugar molecules gumming up the works?

Obviously you already knew this from your question.

Not using other sugars will help. You might also try adding more sugar to the recipe at the beginning to fully saturate your solution. The fact that you add sugar at the end and it still dissolves in makes me think your solution could take a bit more. Letting the solution cool slowly with your seed sugar at the end should help.

You would think it would be easier to get it wrong. Perhaps you simply have too much experience doing it right.

Ask an amateur to try out your recipe and see if they fail properly.

Be careful of substituting agar or any other "firm" gelling agent; you're likely to end up something closer to Turkish Delight and agar in particular has the property of syneresis (meaning that your gummy candies will dry up fast).

I can think of a few things that would alter the consistency of a gelatin candy/dessert:

• First, it is very important to let the gelatin bloom. When it says to "soften" it in cold water, you need to let it sit there for a good 5 minutes or so until it has absorbed plenty of water and you can actually see a gel forming. Don't stir it at this point!

• All gelatins are not created equal; you need to look at the bloom strength. I think the most common kind in supermarkets is Knox, which has a bloom strength of 225 and is usually what most gelatin recipes calls for. "Platinum" gelatin (normally sold in sheets) goes up to 260, "Gold" is generally around 200, "Silver" is 160, and "Bronze" can be as low as 125 - practically useless for this. If you managed to find powdered gelatin with a bloom strength of under 200, you would need to increase the quantity or else end up with jelly.

• Although gelatin does not require particularly high temperatures to hydrate, you do need to heat the solution to at least 50° C before you set it. If you don't do this, it won't dissolve properly.

• When using powdered gelatin, you're normally supposed to bloom and dissolve it in the same liquid. The recipe you have seems to call for chucking the bloomed gelatin directly into your syrup; this may be deliberate in order to produce some effect I'm not familiar with, but it sounds like an oversight to me. Instead I would heat the gelatin/water solution up to 50° C after blooming (as described above) and then add that to the syrup.

• Finally, as Computerish says, make sure you're heating the syrup solution enough to get all the sugar dissolved, and you might even need to reduce it a little (let it simmer). The more you reduce it, the more viscous the syrup itself will become (at the extreme end turning into pure caramelized sugar, which is rock-hard). So if you're absolutely sure that you are using the gelatin correctly, this would be the next line to pursue. If the syrup is actually syrupy at room temperature then it should form great chewy gummies, but if it's watery then you're more likely to end up with Jell-O.