Replicating Footprint Casts using Latex Molds ...

By Scott Schubbe

Carefully peel the latex off of the original cast, and don’t pull too hard or you may stretch it out of shape. Carefully work it off. Set the latex inside the shoe mold cavity, and you can see from this picture that you are ready to make your replicate cast.

Fig. 5 – Latex mold inside the shoe mold cavity

Here are the three parts, the original cast, the latex mold, and the shoe mold. With the cost of the plaster and the latex, it cost roughly nine dollars for the 2-part latex mold, versus fifty for the silicone. You can only get two cast molds out of one gallon of silicone, and you can get 2 molds out of one pint of latex.

Fig. 6 – Three parts of the process, original cast, latex mold, and shoe mold

Creating the Replica Cast:

The next step is to pour your dental stone into the latex. I use a generic Hydrocal for my copies. Make sure the latex mold is fit where it should be in the plaster shoe mold. I usually pour it with the shoe mold on top of a folded towel, so you can keep it level, or push an edge of the towel under one end to keep it level.

After mixing about half of the dental plaster you will need, slowly fill the mold. I choose to not use any release agent here either, and I have never had any problems. Coat the entire bottom surface, filling it about half way. Tap the shoe mold or vibrate it to let any air bubbles move to the top.

I usually let this set up and semi-harden, before mixing more dental plaster and filling the mold. I use an aluminum wire hanger, so the cast can be hung on the wall. Waiting and letting the first half semi-harden will ensure that the wire hanger does not sink all the way down and show on the front of the cast when you are finished. The best wire to use is the kind they make for chain-link fencing. It comes in pre-cut lengths, and is reasonably priced for a bag of a hundred of them. Metal wire will rust terribly with some dental stone products, such as Hydrocal.

Mix the rest of the dental plaster and finish filling the mold, and insert the wire hanger if you wish to have one.

Fig. 7 – Dental plaster poured into latex mold

Just before your dental stone hardens in your mold completely, it is a good idea to scratch the data into the back of the cast. Some people choose to write it on with permanent marker, but I like to use a small Phillips screwdriver to engrave the data into the plaster. The data I like to include is, who originally took the cast, where it was taken, and the date first taken.

Hydrocal, Ultracal, and other dental stone plasters all harden at different speeds. I usually leave the cast in the mold for a few hours longer than when it appears to be set up. That way, you won’t mess up any detail on the front of it when you remove the latex from it. Turn the shoe mold upside down over the towel, and let the cast fall out of it. Gently pull the latex off of it, and let the new cast dry for a day before you hang it, or pack it up to ship, etc.

I find that both materials, silicone and latex, work quite well, and capture even the tiniest detail from the originals. But latex is far cheaper, and since it will last longer, there is no question what I will use from now on.

Here is the copy on the left next to the original cast. Thanks to Cliff Barackman for showing me this method.

Fig. 8 – Copy on left, beside original cast