This Instructable shows my technique for using Instamorph to make a thimble that actually fits and stays on my finger. I have sewn costumes for many years and can never find a thimble that really fits my small fingers. This one does.
--Pre-made flat sheet of Instamorph approximately 1/8 inch thick by 2 inches long by 3 inches wide (adjust the size based on the size of your thimble finger and how long you want the thimble).
-- A bowl or pan of hot water (to re-soften the Instamorph as you work it).
-- Scissors (Not the scissors you use for cutting fabric!)
-- A metal fork or skewer for making indentations in the end of the thimble
Step 1: Prepping the Flat Sheet of Instamorph
Cut a flat piece of Instamorph to the approximate size needed. Place it in a bowl or pan of hot water to soften it. When it becomes clear it's ready to use.
Step 2: Mold the Thimble
Wrap the sheet of Instamorph around the finger that will use the thimble. Be careful, as Instamorph just out of the hot water is...hot! You can let it cool slightly and still have a minute or so to work with it as it starts to harden. Place the pad of your finger near the middle of the sheet and pinch the sides together along the back of your finger. Pinch the end closed over the tip of your finger.
If you want a longer thimble, be sure to bend your finger slightly (in the position you are likely to use it) so the Instamorph forms to the shape and curve of your finger. I made this one to go just past the first joint of my finger. The advantage of the slight curve is the thimble doesn't slide off in use.
Keep molding the Instamorph to get the shape you want. You'll need to re-warm it a couple of times until you have the size and thickness you want. It's best if the Instamorph is fairly thin except for at the tip of your finger. You will end up with excess material in a ridge along the top of your finger. We'll deal with that in the next step.
Step 3: Trim Excess and Final Shaping
Re-warm the thimble and use scissors to trim off the ridge of excess Instamorph. (Instamorph is reusable, so save your scraps).
Warm the thimble again and smooth out the surface and the bottom edge until the thimble is to your liking.
Step 4: Finishing
Warm the very tip of the thimble in hot water and press a fork tine or end of a metal skewer into the softened Instamorph to make indents-- these will stabilize the end of your needle when working it through heavy material.
The photo with the brown spots shows the indents (filled with cinnamon for visibility). Make as many indents as you need.
This thimble has worked well. When I make another I will make the walls of the thimble thinner and possibly experiment with ventilation holes in the side of the thimble (your finger will eventually sweat since it's encased in plastic). The beauty of Instamorph is that you can rework it as many times as necessary.