A question about interfacing

[snickersnack]

I bought some from a local fabric shop today ? have cut out a very lightweight cotton pattern for a sundress for dd already. This is my first attempt at sewing (so I will doubtless be back with more questions).

Do I need (really need) to prewash it? I am fairly sure the answer is yes, but I was really hoping to get on with it this evening, and if I have to wash and preshrink it (and the fabric) I won?t be able to do. If I do, can I (gasp) tumble dry it, or is that completely crazy?

Sorry, that wasn't very clear. The interfacing is fusible - I was wondering whether that needed preshrinking. I've washed the cotton already.

It's probably fine - this is very much a practice dress, I'm assuming there will be plenty of mistakes...

no you don't need to wash it first

Definitely don't wash it first!!

I didn't wash it, as was too impatient (but have washed the rest for next time). Seems ok, though who knows what will happen when I wash it.

The dress is so cute. I'll have to take a photo and upload it - I'm really impressed with myself. I'm fairly sure my Granny would be horrified at the quality of some of the seams, but it looks fine from the outside, and dd was very taken with it.

Am now planning something more elaborate - possibly with sleeves...can see this might become addictive.

I never wash any material before sewing, apart from denim, that does need to be pre-shrunk. Otherwise, just sew with it. The interfacing will have lost its abilitiy to be ironed on, otherwise it will be ok. It did not need pre-washing.