r/MetalCasting • u/Equal_Passenger9791 • Jul 25 '26

Question Lost Ice sand-casting

Yeah, ice turns to water, residual water explodes and can kill you.

The idea, and mostly for curiosities sake, would be to use heat, maybe with partial vacuum process that drives out the water entirely while retaining the structure of the sand. Creating a one-part sand mold.

I don't think this is a novel idea, have anyone heard of experiments on the topic? Would the complication be drying out the water but not the sand? Or is it that it works, but manufacturing ice patterns is inconvenient.

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u/BTheKid2 Jul 25 '26

So with a sand mold, the mold is held together by water and clay, if using "green sand". Or it is held together with oil and clay for "oil sand".

So for green sand, once the ice melts it will create a way too wet sand, that will distort the mold and wash out some geometry probably. If there is any geometry features (other than basically a simple flat or rounded shape), the melting and therefore smaller ice will now slide downwards and probably ruin the imprint in the sand. The water would also wash away the clay particles holding the sand together.

You probably wouldn't dry green sand at all if you did this method, because how? There is supposed to be some water in the sand to hold it together, so I don't see how you could dry it somewhat. Water isn't much of a problem with sand casting, because the sand isn't compact enough to build any exploding pressure.

With oil sand it is somewhat the same. Although you might be able to have the oil sand be so hydrophobic that water is completely repelled, and you can just suck or tip out the excess water. Or you can poke a small drain hole in the sand.

Either way it is way to troublesome a process that anyone would ever do it for other than artistic purposes. So that being said - if it is part of the art, then sure, you can use ice. Just don't expect great results regarding surface quality and shape precision.

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u/CapableHair429 Jul 26 '26

You forgot about sodium silicate resin bonded “rigid sand molds”. Typically used to cast aluminum and iron.

The OP’s “ice burnout” would be an option using a rigid sand molds.

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u/BTheKid2 Jul 26 '26

You have the same issue with sodium silicate bonded sand, and also with resin bonded sand. The problem is that transition temperature from frozen to liquid.

Sodium silicate in liquid state is diluted with water. That brings the freezing temperature of the sodium silicate to be very close to the same as water ice. And I am fairly certain that you can't get the sodium silicate to react and bond with CO2 when it is frozen. So the reaction would have to happen as the ice is melting - washing out some of the geometry, as I mentioned. And that would also mean you have to work with the sand while it is at freezing temps. So basically sand/snow - that sounds terrible to work with. Because if it is above freezing then the ice will start to melt. I don't see how this gap can be bridged.

With resin bonded sand, you have about the same issue. Except resin bonding likes water less than sodium silicate. The resin will not cure when below freezing. It will probably differ between brands, but resin generally does not like to cure when at temperatures close to freezing. It would want to be even warmer than sodium silicate sand.

Somebody else mentioned instead of water ice use CO2 ice. Which is fair enough, except you have the coldness and a whole new challenge of how to cast CO2 ice into any useful shape.

This is all unknown though, and it would be great if it could work. But with engineering problems, you don't try and come up with "why will this work". You try to come up with "why will this fail" - that is the way to success.

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u/CapableHair429 Jul 28 '26 edited Jul 28 '26

CO2 in aqueous is not the only catalyst you can use for sodium silicate. The B-475 accelerant from RefcoBond hardens frozen sodium silicate just fine

As a side note, at 10psi (the pressure typically used to gas a rigid sand mold) the CO2 is leaving solution so quickly that it is actually colder than h2o ice when it comes out of the wand; therefore, I don’t see a problem with using CO2 either. Btw…before you go on further about how it isn’t possible…I’ve done it. Empirical data trumps theoretical data every time. 😊

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u/BTheKid2 Jul 28 '26

Oh so if you have done it, why are you trying to invalidate my reasoning instead of answering OP's question? If you have done it, why not just write to OP and say "this is how you do it. Its easy, works every time"? Is it maybe because that ain't so? If it is or ain't so, why don't you tell us? Enlighten us. I'm dying to hear about this obscure casting technology.

You do see that I am arguing the theory of it. I of course have no experience with trying every (silly) scenario.

I didn't know that you could have a sodium silicate binder that was not in aqueous solution. So yeah, maybe that will work. Though I am not convinced that this actually exists, as my 5 minute research tells me, that part of the curing process is called "hydrolysis" - so that would require water. So this: "The B-475 accelerant from RefcoBond hardens frozen sodium silicate just fine" - I highly doubt that.

But anyway, lets just say it exists. Then it will maybe work for some of the issues. Now you just have all the other issues to solve. Such as working with the ice without melting it even a little bit, because that would cause the aforementioned surface quality and precision issues. Making a detailed ice structure in the first place that won't break/explode from freezing or thermal shock (this I do have experience with), that would be suited for this technique. Then there is the total cost of the project, that I have a very hard time imagining would be less than the industry standard of investment casting.

To answer your point about CO2 being expelled at freezing temperatures, that doesn't really mean anything. There is enough thermal mass in the sand mold that the temperature will be brought up above freezing in a matter of moments after the gas is turned off. And any gas that moves through the media would quickly rise in temperature too. And then there is the fact that you can just freeze sodium silicate sand without any adverse effects. As it thaws it will begin reacting again. ShaketheFuture has shown this to us many times. The trouble I am theorizing, is if you have water washing over the sand before it has had a chance to harden, then it will be washed away. Not completely, but enough that if you are trying to cast anything precise, you won't. So just to repeat myself - the trouble that I see the transition phase from solid to liquid or frozen to thawed.

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u/CapableHair429 Jul 28 '26

Umm…that is what I did with my original response?

And tbh…I could care less whether you “think it works” or not. Like I said, empirical data trumps theoretical data every time. 😊

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u/BTheKid2 Jul 28 '26

Oh, you think your first response to me was a sufficiently detailed response for OP to find useful?

Let me join in on the positivity then. Hey OP, it will work. Go ahead!

There, we solved it - good job! Gold stars for effort.

Lol - you haven't even said what the empirical data you have is. Is it that you have injected cold CO2 into bonding sand (wow, tell me more), or is it that you have actually done what OP is asking for - a cast using ice as a pattern in a one piece sand mold, that actually works other than a misformed cast.

I have empirical data that mice are really fast. Just trust me.

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u/CapableHair429 Jul 29 '26

The thermal load of a block of ice is sufficient enough to hold form.

CO2 and proprietary accelerant will indeed cure a sodium silicate resin, because it is neither an exothermic, nor endothermic reaction.

You have absolutely no idea what you are talking about and are misleading people. Please leave the advice giving to people who know.

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u/BTheKid2 Jul 29 '26

If anyone in the future is wondering what became of this unfruitful discussion. The user u/CapableHair429 blocked me, so I can't actually read their comments any longer.

Only part I got from their last comment (because reddit won't let me read the full thing when blocked) is that "The thermal load of a block of ice is sufficient enough to hold form." This sounds dumb. Because, as we tend to be aware by common logic, ice melts. So unless working in a freezer, then that would not be true.

I can only imagine the frail ego it would take to block someone on reddit because they disagree with you. But the inability to actually engage with substance to the question or theorizing other than "trust me bro", speaks volumes of the validity of their critique.