Finding the right underlining for taffeta (anything, really) can be a challenge. Last night I was discussing this with my friend, Bridget. She's a buyer for Renaissance Fabrics, and she mentioned they have a new 60" cotton twill that flat lines taffeta beautifully.
19th Century bodices need a lot of under support to hold the bodice in shape, be sturdy enough for boning, and create a firm base for trims. Twill fabric works best for this garment. You can also use a denim or tightly woven poplin as well. Remember, for best results, use 100% cotton or linen or a blend of the two for your underlinings.
So check out RF's new twill for flat lining your latest ballgown bodice. Tell them you heard about it from Cloak & Corset!