Shoe "last" From Plaster Casting, Weight On Foot?

[Softanvil]

Hi! I'm sort of following up on this idea: http://greencouple.com/2009/03/08/shoemaking-102-making-lasts/

However, I'm going to modify the casting to make it into a last and not just a foot replica. I might have the casting 3D scanned and then modify it in 3D studio and then remake it with a CNC mill, or I have some similar ideas. But first I need a cast of my foot.

Now, my question is, when making the cast, should I put my weight on this foot so that it is pressed against the floor like when I'm standing up? That will make it slightly wider and flatter.

Or should I suspend the foot above the floor and then make an impression of a "neutral" foot?

[electrathon]

Lasts are not really the shape of a foot, but a guideline to the shape for support. The best example of this is that a shoe is longer than your foot is so that your toes do not touch the end (at least they shouldn't) but they do touch the sides.

But to answer your question, measuring of the foot is done with some weight on the foot, for the reasons you said. I have othotics insoles that the Dr made from a cast of my foot and he did the cast with no weight bearing. They are not really the exact shoe size though, you often have to trim them depending on the shoes you wear.

[Softanvil]

Lasts are not really the shape of a foot, but a guideline to the shape for support.

Yes, that was my point with "I'm going to modify the casting to make it into a last and not just a foot replica"

But I don't understand your answer. If measuring is done with some weight on the foot, but your othotics were cast with no weight bearing, what does this mean?

The reason I'm asking it that those casting socks are kind of expensive, so I'd like to get it right the first time. Should I start my last making from a cast made from a neutral, free-hanging foot, or while standing on the foot?

[Softanvil]

And I do understand that it will be difficult and I'll be lucky if I make a decent last on my fifth iteration. There is no rational reason that I don't just buy a ready made last or indeed a ready made shoe; this is all for the hobby value only.

[electrathon]

When I took shoe making class we were told that measurement of the foot to properly fit the last the foot is placed on the floor to measure it. But, when I had orthotics made it was done with the foot suspended. Use tights/thick pantyhose as the sock that you cast over. Very cheap.

[Softanvil]

Ok, I'll try using some weight on the foot then.

I don't think you can use pantyhose in the same manner as the casting socks in the link in the first post? These STS Casting Socks are made from 5-minute PU. Alginate would be a much cheaper if making multiple moldings, but for a one-off, the STS seemed much less hassle and less cost. I got mine for £20 / 1 pair.

[electrathon]

To go low budget you can use pantyhose and cover your foot with plaster casting material just like old school broken bone casting. Even cheaper use 20 minute hot mud for fixing walls and dip stranded newspaper in it. You can treat it very similar to how he was working in the article. For a few dollars you would have enough material to do multiple castings.

[Softanvil]

Thanks! That is a great tip!

[electrathon]

Post updates as you proceed. I am interested.

[Softanvil]

By the way, I'm considering following another bloggers idea and making a "resin last", by sticking modelling clay onto a plaster casting of my foot, shaping it into a last, and then making a new negative mold from this. Then I'll fill this negative last mold with resin and extract a last.

Do you have any recommendations on what type of resin to use here? I'll probably stick a "wooden sole" onto it for putting nails into when using it as a last.

Edited July 28, 2013 by Softanvil

[electrathon]

I didn't mention this earlier but I have a very messed up foot. My reason for learning to make shoes was do that I could make shoes that lessen the pain I have walking. I am currently working on my second and third pairs, one pair will be similar to the first pair we made in class and the other will be made using a pair of Birkenstock repair insoles. I have the lasts for the first pair. The Birkenstocks have a very oddly wide front to them, so I have ordered a pair of EEE wide lasts and I am going to reshape them narrower. I can also add to the toe area by laminating leather and then grinding it to shape. As to using resin, I think it would work. You will likely be using fiberglass epoxy resin, it is available and not too expensive. You will have to be careful driving lasting nails into it, so a wooden bottom may be good. But if you use a wooden bottom you will need to hand carve the bottom to be foot shaped, if that is what you are trying to do. Normal shoes are nearly flat on the bottom, having a slight arc left to right.

[Jazznow]

When you want to make a last, you want to stand while making the form. Put a piece of wood under your foot that has approximatly the same thickness as the height of your shoe heel. That will ensure that the last had the same angles as the foot when it's in your shoe.

You don't need to use this expensive casting socks. A ordinary plaster bandage will work too and they are less expensive. Just make sure you have someone that helps you forming it to your foot.

Best wishes

Edit: don't forget the plastic bag. It really hurts when all your hairs are stuck in the plaster

Edited August 14, 2013 by Jazznow

[Woodyrock]

Industrial paper towels cut into fours, dipped in plaster work well, but you need someone else to do this whilst you just stand there. I have Birkenstock shaped feet, so real shoes are problematic. I made lasts by first making a plaster casting, adding plaster to shape it as a last, then used the plaster to make the last from wood on a duplicating carver. Shoes look like crap, but they do fit, and are comfortable. You only need about 1/4" of plaster/towel to make a good mould. I have done full torso casts using this method.

Woody

[Hennie]

I also make custom made shoes. When doing that, I use the clients foot as last with a spacer under the toes in order to create enough toe room.

[feedbag]

In my last life I was a shoe maker for challenged feet, I would sit the client in a chair with the knee flexed at 90 degrees and a wedge type device under the foot to simulate a slight heel ht. I would also flex the toe up slightly to create a rock for break-over of the foot during push off. As far as casting materials go (there are many) you can use nylons with a flexible tube over the instep then use four inch plaster wrap message well,form the casting material to the foot , the tube on the instep and slight flexion at the toes then bend the knee to 90% and place the foot on the wedge (platform) wait till hard then cut along the tube to clamshell enough to get the foot out.

[Softanvil]

I got stuck with a defective pair of casting socks, and that put me off for a while. I did try making a mold out of plaster, by coating it with PVA glue, then another coat of laquer, and then I applied vaseline to that before filling it with plaster for the cast. It worked pretty well, but I only made half inch high casts of my footsoles. These were very useful for making hotglue barefoot shoes. My intention was to continue making another two pieces of mold for a 3-piece mold that would separate nicely, but eventually discarded the idea, as I began looking into getting my feet 3D scanned instead, and ordering a regular shoe last. After all, a cheap way of making a last can quickly become pretty expensive when you need to work out the process from scratch...

The main problem was that it has become very hard to find the materials where I live. In the past, there were a lot of hobby shops and hardware stores catering to small companies selling small quantities of stuff. Nowadays I would basicly have to order industrial quantities directly from the manufacturer (in China...). I couldn't even find stuff like quick setting hotmud in less than 50 lbs bags, and I don't know any carpenters. Same thing with polyester and epoxy; hardware store only carries stuff made for applying sheets of fibreglass to boat hulls, and it specifically says you can't pour it for casting (it won't harden). And alginate for foot molds would have costed upwards of $150 because it seems only food grade in pound bags is sold here, probably due to regulations.

So for making a one-off, it doesn't seem to be economically viable. Eventually I think I will just order a CNC wooden last.

Edited November 12, 2013 by Softanvil