My son's class signed t-shirts with various types of markers and pens?

India ink did the job for me. I drew pictures on a dresser scarf and went over it with a pen dipped in India ink. {It did not run or make ink blots outside what I put it on.} Then what you do is go over it with a hot iron. It lasted for over 5years but we moved and I lost it.

That depends somewhat on the kinds of pens/markers used, and how you care for the shirt over time.

Some markers and pens are "permanent," some will wash right out just with water. Some will be permanent but may change color a little when washed. Most, but not all, will fade with washings and perhaps with excess sunlight.

I'd suggest you do a little tiny water/smear test on each of the signatures. For the ones that don't look totally waterproof, go over each with a pigment pen (Pigma, etc) or "fabric pen/marker" (any brand) since those will last the best.

Then give the shirts a week before washing to allow as many as possible to "cure" as well.

You can also put a thin cotton cloth ("press cloth") over the shirt and heat all the areas (don't iron back and forth, just pick up and put down a "dry" iron on all the areas for at least 5-10 seconds), which could help some of them (you can probably also just do that from the inside side of the shirt).

When washing, don't use a harsh detergent like Tide. Use a gentler one like All or Cheer, I think, or even better just use soap or Woolite (hand or machine wash).

All those things should help.

Another possibility, though fiddly and time-consuming, would be to soak the areas with the non-permanent inks with something called "textile medium" to encapsulate and seal it onto the shirt. Textile medium dries clear, and is used to mix into regular acrylic paints when used on fabric to make them softer and more supple than using acrylic paint alone. They're found near the acrylic paints:

http://images.google.com/images?q=textile+medium

You might want to do the first coat from the back side of the fabric (not a heavy coat) to help fix the ink on the front side, then do the front side lightly. Then perhaps go back and really soak to seal.

(Hairspray would either wash out immediately, or would make the shirt sticky and/or stiff in areas... acrylic spray or artists' fixative would be possibilities --even for that first coat to just seal a bit-- and would seal better but may also be stiff.)

The hairspray will delete the ink BEFORE you wash the shirt. Hairspray is often used to dissolve ball-point ink when nothing else will work.

Depending on how much effort and expense you want to put into preserving the signatures, you could do some or all of the folllowing:

Set the ink with white vinegar.

Set the ink with Retayne (http://www.amazon.com/Retayne-Color-Fixative-4-Oun... ).

Go over the signatures with the same color of ink that you know to be permanent and appropriate for cotton fabric.

Go over the signatures with the same color of fabric paint.

Embroider over the signatures.

You could buy one of the sharpie fabric markers (There called Sharpie Rub-A-Dub) that don't ever wash out and then just go over the signatures. You could also dry clean it but that's alot just for a t-shirt.

Tshirt Pens