I learned this technique in grade school in 1940's. Still works for me today. We set our colors by using wax paper on top of design and ironing over wax paper. Now today more color choices sure are nice.
SQ
I just iron on the wrong side to set it using paper towel so it doesn't get on the ironing cover.
We were told wax paper helps lock color into fabric and towel underneath prevents transfer to ironing board cover.
SQ
Very pretty. What did you paint this on?
Lovely. Have you tried colouring in embroidery designs with them?
I have done this type of coloring using redwork type designs...it works well, but you need to be careful about laundering as the colors sometime fade...even with heat setting...same with colored pencils...I have now moved to using fabric pens as they are much more durable and long lasting.
I think it must depend upon the brand and the tip size of the pens....the type of fabric can also be a factor...