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How to: Make Homemade Molding Putty

Started by FABphones, February 24, 2022, 03:47:48 AM

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How to: Make Homemade Molding Putty


Tube Silicon Sealer
Corn Starch OR Talcum Powder (see below)


Chaulking Gun
Board to work on
Cling Film (wrap it around the board)
Latex Gloves (or similar, I use powdered)
Small Mixing Spoon (or similar)

The wet/dry ingredient ratio is 50 / 50.

1-  On your prepared work surface place the amount of the Dry Ingredient you think you will need to thoroughly cover the piece you wish to cast (allow approximately 1cm thickness).

2-  Make a well in the middle and squeeze in an equal quantity of the Silicone.

3-  Start mixing. Wearing gloves, mix the ingredients thoroughly together until the sticky feel has gone. If it still feels sticky once mixed, add more Dry Ingredient. Some folks mix the two ingredients directly in a plastic bag; I prefer the hands on approach, less waste in the bag and easier to feel when consistency correct.

The putty is ready when it rolls into a nice none sticky ball. Not dissimilar to a soft dough.

4-  Mold your item immediately.

That's it! Super easy!


Corn Starch vs Talcum Powder

Corn Starch: shorter time to work the mix - approximately 15 minutes, dries faster. Mold can be turned out within 20/30 minutes. Medium flex mold.

Talcum Powder: smells nice, longer working time, overnight drying time (my preference for this mix). Softer flexible mold.

This molding putty is suitable for smaller piece casting. The molds are good for several uses depending on the item being cast and the casting product used; eg plaster, resin, hot glue. For ease of use, Milliput leads the way for many telephone projects.

Casting material depends on the end purpose of the cast piece, this example shows air drying modelling clay. The molds are strong enough to withstand the clay being pushed into the nooks and crannies, and flexible enough to bend and help release the molded piece.

Modelling clay requires no release agent. For other, I use an Aerosol Wax to prevent the molding medium from sticking to the putty mold. It is also advisable to spray the item from which you are taking the form as well. As you can see from the mold I made, even with a release agent some of the gold surface of the master piece adhered to the putty.

NB: As these are Silicon Molds, a Silicon release agent will act as an adhesive, be careful when choosing which product.

The example mold shown was made with a 50/50 Silicon/Talcum Powder mix. As I was only casting a small part of a larger design I needed the flexibility to remove the mold without damage. I made seven casts and the mold is still good to make a few more if necessary. More work will be done by hand on these pieces to further tidy them up.

Although destined for the new telephone room, as these examples aren't telephone casts I will next update this thread when I next cast a telephone part using this method.

Hope this 'recipe' comes in handy for you. Happy casting!
A collector of  'Monochrome Phones with Sepia Tones'   ...and a Duck!
Vintage Phones - 10% man made, 90% Tribble


Good to know, thanks!

I am pretty lazy though; I just buy this stuff and mix it together when I need a tiny mold. I also know these people (the mfr) and they are only about a 60-mile drive from my house. Spending time at their factory really helped me when I was trying to learn how to cast phones & parts.
Ray Kotke
Recumbent Casting, LLC


Thank you for the detailed description & experiences FABphones! That sounds like a good plan for occasional projects without the need to buy expert grade products.


QuoteThank you for the detailed description...

You're welcome.  :)

It is a fun make, and works surprisingly well.

I forgot to add an image of a finished cast piece in place in the Phone Den, now attached below:


Zoomed out image on this thread:
A collector of  'Monochrome Phones with Sepia Tones'   ...and a Duck!
Vintage Phones - 10% man made, 90% Tribble