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Problems with delft clay casting Answered

Hi. I'm pretty new to delft clay casting. I make my models out of sculpey clay.
2 problems I'm having: 1: sometimes the clay sticks to the model in the fine details (small letters, curves, etc) 2: takes SEVERAL attempts to get a good pour to fill the mold. I'm making several air holes and a pretty good size pour gate/channel. Any advice? Thanks

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bdanielpa2019

25 days ago

I've tried dusting the model....doesn't work
I've tried oiling the model.....doesn't work
I've tried delft clay and petrobond. Both stick
This is the size of the model. Delft clay gets stuck in the letters

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Downunder35mbdanielpa2019

Reply 25 days ago

That explains a lot.
The model itself is far from being perfect.
You will have areas where material gets trapped or that are just too uneven.
If it is not that important then try my old candle trick:

For really bad originals I either make a silicone model or mold first - or take the shortcut.
Wax does not stick to much, is easy to use and work with.
Only problem is the stuff is hot when you have to heat it.
For a first test:
Prepare enouch liquid wax to submerge you part.
Clean your part with quite warm soapy water and a soft brush.
Dry it with a lint free cloth or paper towel quickly - if the thing can absord water then wait with the wax and let it dry properly in warm oven or sunlight.
You don't want to mix any remaining water with hot wax!!!
Either way once fully dry and still quite warm cover it fully with wax.
Let all excess drip off, if doubt use a hair drier to use the hot airflow to push away what you don't need.
The resulting wax coating should be extremely thin and if tested on the back with your fingernail then next to nothing should scrape off.
Very tiny imperfections, cracks and such however fill be filled or at least smothed out.
Your project might now succeed.

If it still gets stuck it mean you have areas that form an undercut or areas where material gets trapped.
Use a lot of light a magnifying glass and have some quickly made poking, scraping and smoothing tools ready.
Wherever you spot an area of trouble use some warm and soft wax to fill or smooth it out.
Some tiny hobby knife blade or metal strip can be heated quickly over a flame and then create a perfectly smooth surface on the wax.
Little marks you might create along the way canbe fixed the same way or by "dunking a flame" - a lighter or match quickly placed and removed usually smooths out what it left.

Once done and satisfied you can heat up the model and wipe off most of the way, leaving a protective coating.

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Downunder35m

26 days ago

Try to dust the mold with corn starch, blow out the excess.
And if you have no intentions to paint it then spray oil works well too.
Cooking oil can be cleaned off, silicone oil is better but impossible to glue or paint the cast when done.