Sodium Silicate for Foundry Sand

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SmithDoor

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Most know about using sodium silicate for making core but it can also be used for molds too. Dry ice can use to set the sodium silicate. Do not put Dry ice a container or touch the Dry ice. It builds pressure over 800 psi and will burn your skin is so cold.

Place the Dry ice top sand and cover with plastic tarp. Then let setup


Both can found in local stores.

Great for just few good castings.

For a crucibles pipe cap it will not last a long time but can found at local stores. You need to make a handle to pickup the crucible.

The furnace can be a old charcoal BBQ and steel tube/pipe from a vacuum cleaner.

Parting powder just use baby powder.

Please be safe I did not cover the safety need in the foundry.

Dave

Mixing can done in a plastic bucket. Note is will setup without CO2 so use a bucket or container that can be through away.
 
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GreenTwin

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A word of caution about putting dry ice in a closed container.
The pressure can soar to over a thousand pounds in just a few minutes, causing the container to fail in a very dangerous way.

.
 

SmithDoor

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A word of caution about putting dry ice in a closed container.
The pressure can soar to over a thousand pounds in just a few minutes, causing the container to fail in a very dangerous way.

.
You do not put container
It place in top sand and cover with plastic tarp. Then let setup

Dave
 

SmithDoor

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A word of caution about putting dry ice in a closed container.
The pressure can soar to over a thousand pounds in just a few minutes, causing the container to fail in a very dangerous way.

.
I did edit on how use dry ice 🧊
Thank you
Dave
 

SmithDoor

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Where to find


Walmart

Amazon

Dave
 
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kiwi2

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Hi,
Not sure but I don't think putting dry ice in a closed container will build pressure to over 1,000 psi. As the pressure rises the CO2 gas will liquify. The pressure over liquid CO2 will be 75psi.
Regards,
Alan C.
 

GreenTwin

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Hi,
Not sure but I don't think putting dry ice in a closed container will build pressure to over 1,000 psi. As the pressure rises the CO2 gas will liquify. The pressure over liquid CO2 will be 75psi.
Regards,
Alan C.
I saw it happen on a foundry forum.
I can't explain way, but he posted a picture of a pressure gauge reading over 1,000 psi.
He was lucky he relieved the pressure before his bottle blew up.

Be safe out there if you try doing casting stuff.
Better safe than sorry.
.
 
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SmithDoor

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I saw it happen on a foundry forum.
I can't explain way, but he posted a picture of a pressure gauge reading over 1,000 psi.
He was lucky he relieved the pressure before his bottle blew up.

Be safe out there if you try doing casting stuff.
Better safe than sorry.
.
If is very unsafe to put Dry ice in a container.

I am use dry ice on top of the sand to set the mold.
Even compress air will set the sand.


If just let mold set on table it will harden take less than week.

Dave
 
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I am very interested in trying sodium silicate with fine dry casting sand as a mold material. Same idea as lost wax and plaster, using 3D printed models. If you set up the sand with CO 2 could the mold then be heated to burn out the model? Would the silicate sand hold together or would heating destroy the bond?
 

SmithDoor

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I am very interested in trying sodium silicate with fine dry casting sand as a mold material. Same idea as lost wax and plaster, using 3D printed models. If you set up the sand with CO 2 could the mold then be heated to burn out the model? Would the silicate sand hold together or would heating destroy the bond?
The heat reduce the bond .

Dave
 

GreenTwin

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They also make a catalyst for sodium silicate, and the catalyst hardens the SS, in lieu of using CO2.

Last I saw, Clay Planet sold the SS and catalyst.

Now I don't see the catalyst on Clay Planet, or anywhere else.

The catalyst is called ChemBond, and you can get it various speeds (if you can find it).
You can get 210, 220, 230, 240, 250 and 260, with strip times ranging from about 80 minutes for the 210, all the way down to 6-10 minutes for the 260.

.
 

SmithDoor

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They also make a catalyst for sodium silicate, and the catalyst hardens the SS, in lieu of using CO2.

Last I saw, Clay Planet sold the SS and catalyst.

Now I don't see the catalyst on Clay Planet, or anywhere else.

The catalyst is called ChemBond, and you can get it various speeds (if you can find it).
You can get 210, 220, 230, 240, 250 and 260, with strip times ranging from about 80 minutes for the 210, all the way down to 6-10 minutes for the 260.

.
It more of a simple way to due casting in the backyard.
Most try clay base foundry sand.
The sodium silicate was use in foundries for very large casting till chemical base binders.

For home foundry not mixer or muller need.
It can done in zip lock bag.
It does take as much sand for mold as Clay base sand and is a lot stronger too.

Dave
 

GreenTwin

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I will mention that you don't want to overgas sodium silicate molds and cores.
A 5 second gas will give a very strong mold or core, and anything more than that can cause the mold or core to be very weak and cruble.

I think Dave meant to say "It does not take as much sand for a mold when using a sodium silicate binder, since the mold is very strong".

For my resin-bound molds, they are often 3/4" thick in many places, which is not something you would typically get away with using green sand.
I often make my flasks so that they follow the shape of the patter, and I sometimes fill in vacant spots with wood blocks, the intent being to use as little bound sand as possible.

A bound sand mold can be perhaps 1/3 or less the weight of a typical greensand mold.
.
 
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I understand that getting a sodium silicate core out of a complex casting can be a problem. I recall something about adding sugar to cores to make them easier to remove. Don’t how much you add or what it does.
 

GreenTwin

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I have heard of others trying sugar with their sodium silicate cores, reportedly with good success.
I am not sure the amount of sugar added per pound of sand, but I would guess it does not take much.

Most folks (myself included in the beginning) over-gassed their cores, which makes them crumble.
To counteract the weak core, people (including me) then added a lot of extra sodium silicate to their sand, which makes the cores pretty much like concrete in hardness.

If you add the minimum amount of sodium silicate per pound of sand (per the instructions, I forget the exact amount; perhaps 3-5%), and gas with CO2 for 5 seconds only, you will have a strong SS core.
To help break down the core, I use water, which weakens it if you use the minium amount of sodium silicate.

Generally, I make both my cores and molds from resin-bound sand.

I may try the sugar with sodium silicate cores, just to see how it works.

.
 

SmithDoor

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I understand that getting a sodium silicate core out of a complex casting can be a problem. I recall something about adding sugar to cores to make them easier to remove. Don’t how much you add or what it does.
Removing core sand is a problem with any type of core sand.
Even on outside cores.

At time use a shell core for rim wheels. The shell would still stick to castings. This fix by no core machining the grove.

Dave
 

GreenTwin

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The old school cores were generally made with sand and linseed oil, and often with an additive to help the core break down after the pour, such as sawdust, flour, etc.
If you are having problems removing your cores, your core material in not correct.
The core should mostly break down as the casting cools.

I have not had a problem removing resin-bound molds or cores.
The resin breaks down in a few minutes due to the heat of the metal, and so the cores crumble on their own, and are easy to remove.

One trick is to spray the cores and bound molds with a mold wash.
I use an alcohol-based spray-on ceramic coating on the mold halves, and the cores, and it stops any burn-on/burn-in of the metal into the sand, and gives a clean, shiny finish on the casting with no cleanup, and no sand adhering to the casting.

Below is an iron castings right out of the mold, and still hot.
A few strokes of a dry paintbrush removed any remaining sand from the casting.
You can see the mold material breaks up from the heat of the metal, and the core should do the same.


r2Img_7743.jpg
 
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solarenergyadventures

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Hi,
Not sure but I don't think putting dry ice in a closed container will build pressure to over 1,000 psi. As the pressure rises the CO2 gas will liquify. The pressure over liquid CO2 will be 75psi.
Regards,
Alan C.
Actually, at room temperature of 20 deg C it will be about 830 PSI.
 

kiwi2

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Hi solarenergyaventures,
You're quite right. I didn't read the Wikipedia article properly. The 75 psi for liquid CO2 they quote is for the triple point at -50 degrees C. At room temperature it will indeed be 830 psi.
Regards,
Alan
 

SmithDoor

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Flasks for sodium silicate can be very simple just wood and L brackets from the hardware store.
This type of molding in for just few parts for making engines parts.

Dave
 

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