A fresh white collar is one of the fastest ways to spruce up your impression. In my opinion, not wearing a collar for a "better" impression should be done with thought and education. It is common (and a nice touch) to wear a neckerchief for working impressions, but not nice enough for a better impression. 1860s collars are almost exclusively white (not off-white, cream or ecru)--the main exception being black for mourning. Collars are not merely decorative (though nothing sets off a nice ensemble like a crisp white collar) but are highly functional. The purpose being that you detach the collar to wash it instead of washing your whole dress. Period laundry practices are harsh and lengthy. It is just much easier and cheaper to wash a small piece of cotton or linen rather than a whole dress--especially if that dress is silk or wool. Collars should be easily detachable, NOT permanently sewn to the dress. When I sew my collars on, I use about 1" basting stitches. It takes about 5 minutes and it's just one of the things you have to do before an event.
Most collars that you see at a reenactment are more bulky than they should be. They should be somewhat fine accessories (really fine for upper class impressions). Lawn, organdy, batiste and other fine cottons (or even linens) are excellent choices. If you only have muslin on hand and can't make it to the store, a one layer (bleached) muslin collar will work in a pinch. Just use Elizabeth Clark's narrow-rolled hem directions and you'll have a lovely collar that you can wear in good health. Double layer collars are way over-represented at reenactments, so I like to use single layer construction for my collars.
What do you like to use for collars? Single or double-layer? Do you even wear a collar? If not, why not? Do you wear anything at your neck?
Further reading (Sewing Academy threads):
"What Options Do I Have For Collars?"
"Collar Tricks"
