The Home Machinist!

I would like to make a core using sodium silicate and harden it in the core box to pick up some fine details, can anyone recommend a release agent?
Thanks, John

Hmmm.

Keeping in mind I have no experience with what I'll propose, is it possible that you could use silicone spray in the mold before ramming the sand? Seems that would discourage the resulting core from sticking.

H

We use CRC silicone spray in our core box to release sodium silicate and sand core hardened with CO2. Our core box and patterns are 3D printed with 175 filament.

Thanks guys, I'll give that a try.
John

P.s. Nice work Chips!

Wish I could take credit for it, but I am a student in this group, so I do help a bit. This is part of the castings for a hit & miss engine.

I still make my patters the old fashion way, out of wood. I'm amazed at the power of the 3 D printer, but I just don't want to make the investment in time and money to learn CAD and purchase the all equipment, besides, this is my hobby, if I was doing it as a business it would be a different story. That being said, you have some really nice patterns and cores, stay with it and learn how. Keep up the good work.
John

If you use it, let us know how the silicone spray works with your wooden core boxes.

While not the topic at hand, I have not great memories of the time I made a pattern and finished it with shellac. The foundry that did the casting used the Furan process, which fused the mold to the pattern. You're wise to be concerned for that reason.

H

I'm not familiar with the Furan process, can you explain it Harold...reason being, I still use shellac to finish my patterns.

Furan is one of the chemical processes that result in a hard mold. Like hardening with CO2 and sodium silicate, the mold is far more rugged than green sand.
While I am aware of the Furan process, I know little about it. I do know that considerable equipment is required for its use. It is reconstituted after use and used repeatedly. It's likely well beyond the ability of the home foundry.

I used shellac on the form I used to pour my tilting reverberatory, and that was a mistake, too. Had I greased it, maybe it would have been fine, but it, too, fused to the refractory. I damaged the furnace trying to get it out and ended up burning it out. A sad day for me, to say the least. Here's a picture of the form, and the resulting furnace, which was used in my precious metal refinery. The furnace was cast with a low temperature external liner (using the galvanized form), then the interior liner was placed, using the wooden form. The interior liner was 94% alumina. This furnace had to withstand excessive fluxing on a continual basis, as it was used to recover values from waste materials. It operated for hours on end, and worked like a champ!

H

It took me this long to finish the pattern that I wanted to make. The silicone spray seems to work as a release agent, but my core broke up as I was removing it from the mold, I gave the back of the mold a sharp rap and the core busted all to hell. After gassing the sodium silicate/sand mix I noticed it was very cold, so I'm letting it warm up to room temperature before I try to remove the core. I'm using a 5% by weight sodium silicate to sand ratio, I'll let you know how this try turns out.

It didn't turn out very well.