Any clue why my black and other deeply colored marshmallow fondant is cracking. I use Americolor gel colors.
The batch I was working with tonight started off very sticky still, so at first I just worked in cornstarch to roll it out. Still kinda sticky, yet where it's folded or bend it cracks! Second bit I worked with I used more powdered sugar in it, but there wasnt' much improvement there. I was originally going to make Duff style roses and saw very quickly that wasn't going to work. I managed to get some ribbon roses to look halfway decent. They are going on a twilight cake, so it will be ok.
I have a batch of red made that I will be covering the cake in tommorrow night and I'm afraid it's going to do the same thing!

I don't make black anymore. It either cracks or to get it a true black, is too sticky. I've felt your pain. However the other day I had some light pink cack as I was smoothing it on my cake. It cracked around the top edge so bad, I had to take it off and just threw it away. The only thing I could think of was my marshmallows were a differnet brand than normal, and a month from the expiraton date. The rest turned out fine, even the red-but they were a different brand of marshmallows

Any time you color MMF a dark color there can be issues with the fondant because by necessity adding that color has gotten the ratio out of whack. What I do is add some glucose and knead in a bit more powdered sugar. The glucose seems to bring everything back into proper balance. Just add small amounts at a time and do not be concerned if it gets sticky at first just keep kneading it on a lightly powder sugar dusted non stick surface (like a silicone mat) until it begins to feel as it should.

When you are making black MMF, I find it always helps to make the chocolate version so that you do not have to add as much color. Also, add the color in smaller increments and let the fondant rest. Quite often it will darken considerably. I learned that by easing in with the color I usually use way less than I used to, obtain a better color, and the texture of the fondant is not as affected. HTH

Thanks for your quick replies.
I don't have any glucose on hand. Is there a suitable alternative?

I start with adding some brown, then while kneading start using cocoa powder, then some more brown, then start adding in black. As another poster mentioned, let it rest a bit. I've found that adding cocoa powder really helps. Another thing I've done to get red is to start out with the strawberry flavored marshmallows...then I don't have to add in as much color. You could do the same to get dark brown and black, but start out with the chocolate marshmallows. The flavored marshmallows are a bit more costly then the regular ones, but sometimes it's worth it!

Hope this helps!

Thanks to you all. I used some corn syrup and powdered sugar and saved the red. It was really soft and stretchy, which was a little challenging, but at least it didn't crack.
Next time I will defenitely start with flavored marshmallows or by adding cocoa!