Has anyone experienced this before?

I have always used a particular recipe for gumpaste which works extremely well for me - after curing it overnight its just the right consistency, not too hard/soft to work with. I was using the brand Cal Tylos powder.

But then I made another batch of GP with a new brand of tylose and after curing it overnight it was sooooo hard (almost rock hard, with just a hint of it still being soft inside) that I had to knead it with some shortening and extra fondant I had to make it possible to work with again.

Does this happen with different brands of tylose?

Yes, I had problems with another brand, too, and that's why I will only buy the CAI brand now. I have to go to NYC to get it, because the local shop doesn't always carry it; sometimes they go with another brand offered by a big-named distributor.

Theresa

That's not the tylose I use and my gumpaste is always really soft but sometimes it cracks

I am not sure, if this is completely right. But I always use the same brand. There has been 2 times when is been so hot or maybe in a hurry and my gumpaste didnt turn out as nice..But it can be fix...
For extra hard gumpaste add some fondant.
For soft gumpaste add more sugar..
Edna