How to mold outer shoe sole to the shape of my feet without using a last?

Question

I'm currently sewing my first pair of shoes. They are made of fabric only (no leather, cork or other materials) and a commercial foam insole for comfort. I have covered the insole with matching lining and sewn the uppers to the insole. At this stage the shoes are already wearable, but they lack a waterproof outer sole to make them ready for outdoor wear. My initial plan is to sew the outer sole on with heavy waxed thread, but I might add contact cement if the stitching alone is not enough.

For the outer soles I bought this sheet of 2mm thick material. I experimented with a few scrap pieces and found that you can permanently bend and mold the material if you soak it in hot water and let it cool in the desired shape.

The material is currently completely flat. Joining the uppers to it would result in a shoe that looks like this:

Image source and sewing instructions

Please note that this is just an example of how the shape of the shoes looks like. What is a cork sole in this image would be a rubber sole in my shoes and there would be an additional insole. I don't like this style and would like my shoes to look more like a modern ballet flat:

Image source

The edges of the sole are slightly bent up to give the shoe rounded edges and a more natural foot-like shape.

My problem

I took the pattern directly from my feet (wrapping them in cling foil and then painters tape), so I don't have a wooden last or any substitute. I have to somehow mold the hot sole directly on my foot. The material cools within a minute or so, so I have very limited time to get the shape right. I have no idea how to bend the edges upwards all around the shoe (at least the front 2/3) all at once before the material cools down too much. Does anyone have experience or a good idea how to achieve this?

Answer 1

Here's a way to curve the rim on the rubber. Get a scrap wooden board big enough for each sole, and at least as thick as the depth of the curve. Cut out the shape of the sole. Put the desired curve around the edge (could use a router, but probably fast with just a sander). Make the finished form slightly smaller than the sole (by the thickness of the rubber).

After cutting out the sole shape on the rubber, soften the rubber in a tub of hot water. BTW, this whole process will be done in the hot water, so you don't have to deal with the rubber cooling before you're done.

Form the rubber against the wooden form, working with everything under the hot water (wear rubber gloves to protect your hands). There are several ways to do this:

• Put the wooden form and rubber in a vacuum bag and suck the air out to pull the rubber tight against the form.

• Protect the rubber by adding a stiff but pliable layer on top, something like cardboard cut from a cereal box if you put the whole thing in a plastic bag to keep it from getting wet (would need to temporarily take the rubber out of the water to package it). Then under the hot water with the rubber soft, put very wide rubber bands around the sandwich, one next to the other, so they pull everything together all around. You can do this outside the plastic bag.

• Soak some cardboard to soften it and form it around the wooden form, or apply a thin layer of paper pulp around the form. Let it dry. This will serve as a spacer for the thickness of the rubber. After it's dry, cast a cement shell over it, thick enough to have some strength. When the cement is cured, separate everything, and pull out the cardboard/paper. If some doesn't come out easily, soak it in water to soften it and scrape it out.

  Soften the rubber in a tub of hot water and warm the cement form in the hot water. Sandwich the rubber between the wooden and cement forms and apply a lot of rubber bands around it to pull them together (all done in the hot water).

Whichever method you use, leave it in the hot water for a while to give the rubber plenty of time to conform all the way through. Then take it out and let it cool for several hours so all the rubber in the middle is back to room temperature before taking it apart.