Originally Posted by
Watson
I think setting your seams will correct any small tension problems in your seams by warming and loosening the fibres in the cotton and also allowing the thread to sink in a bit.
I always set my seams, then finger press over before pressing over with the iron.
Watson
That's the reasoning I recall as well. I tend to pre press because (I think) when I don't my seams aren't as consistently flat and laying nicely. Meh, like every sewing thing personal preferences and experiences play into it, right?