What Is The Purpose Of Sew Foam?

[salvisa]

Newbie question.

I've seen people stitch "sew foam" (that stuff that has the scrim or muslin backing on it) onto the back of leather when upholstering a chair or sofa or whatever, but if the chair or sofa is foam itself, why "pre-foam" the material?

[Art]

In car and boat upholstery, it is used as the padding under rolled and pleated upholstery. The only reason it has the scrim or tricot backing is to keep the stitches from pulling through. If you sew foam to leather without the scrim, the stitches will pull through the foam. We used to just make the pleats in the foam by sewing them down. Now-a-days I'm pretty sure you can buy the foam with the pleats in it.

To answer the original question, if you don't sew the foam in, you would have to glue it, which will prevent it from moving a little to help in fitting; and you just can't glue it in when you are pleating.

Art