I iced a cake last night with fondant. the mother asked for stripes. I have never done it before but the pint I used seems to have cracked and now remember I only use this for modelling wish I hadn't forgot. The cake is for tomorrow so there is still time. Question is can I re-ice the cake or do I have to start from scratch.
No need to start again just remove the icing, I did this the other day on a wedding cake. Iced it in the evening, got up in the morning and wasnt happy with it so took icing of and redid it.
I'm not understanding you post Do you mean to say you painted stripes on fondant last night and now it looks cracked?
If you take the fondant off as suggested (Yes, very do-able) you will have to use new fondant because the color used to paint it will color the whole batch.
If I misunderstood and the fondant is all one color then yes, go ahead and remove it; make sure to scrap off any crumbs (wipe w/a slightly damp cloth if necessary); if it's just buttercream that can be left; then re knead, roll and re apply.
I did use fresh icing, not the icing I removed from the cake