I used some of this for my first starch-method applique piece and all the pieces buckled and melted. I guess I was using too hot an iron. I was pressing the edges with my little Clover wand iron and then giving them a final blast of steam with my regular iron.
Then I bought some stuff called Templar and it's very similar - a bit thicker, maybe? Anyway, I turned the heat down for the next block and the Templar didn't melt out of shape or warp. I don't know if it's the different brand or the lessened heat and I haven't tried the other kind with lower heat to see if it stands up as well.
The preparation for this kind of applique is insane - but the results are worth it, aren't they? When my first block was done, I couldn't believe I had made it, it was so pretty. Not perfect, but so precise and consistent - I'm definitely hooked!