You will need:
Access to a vinyl cutter
Silk screen frame
Step 1: Your Image
Get the image on to the computer somehow - take a picture of it, scan it etc. This instructable assumes you know how to get that image onto vinyl. If you don't, find someone to do it for you. Remember to reverse the image. You can see the before and after photos here.
You should now have a piece of vinyl that has your design cut into it and is attached to the backing. It is your vinyl stencil.
Step 2: Peel Off the Vinyl
My first time - once I got going on the letters it went faster
It was hard to tell what parts of the tree image stayed and which ones were to go
The image had many small parts and many thin parts
Next time I would remove the largest areas of the image first, so that I could more easily see the image "appear". Notice that your eye makes a tree look like a tree in this design, but the trunk is actually just a series of vertical lines. Really think about the negative space.
Once all of the vinyl is removed from your negative space, protect it with a piece of sticky paper.
Step 3: Peel Off Backing
Once the paper backing is off, then you need to remove the protective sticky paper. If you did not push the stencil firmly enough onto the silk screen, bits of the vinyl will stay on that paper and mess up your design. That is another reason to use a simple image, there are fewer little bits to attach.
When some bits of vinyl stay behind, pull them off with your tweezers and stick them down on to the silk screen. Amazingly this technique worked and you cannot tell on the final t-shirt where I did this. (Actually, my instructor did this. Did I mention she was very patient?)
Some of the vinyl tore when removing the sticky backing. We were able to stick it back down, and you can't see that mistake either.
Step 4: Final Silk Screened T-Shirts
The good news is everyone loves the shirts and you wouldn't know it doesn't match the original image unless you look at the side by side.
I made it at TechShop!