Experiment: Making Sodium Silicate Sand Cores

One of the options for producing sand cores (used to create cavities in cast pieces) is to mix the sand with sodium silicate (“water glass”), and then expose it to carbon dioxide gas, which hardens the piece enough to stand up to liquid bronze. No fire in this video, just a short materials experiment.
#bronze #metalcasting #bronzecasting #foundry #metalwork #waterglass #sodiumsilicate #bronzeage #sandcores #casting

[@joanmajoor3392]

if you have a bottle of CO2 most probably it is compressed to a liquid ( about 60 bars) so always use them upright to avoid the liquid coming out one only needs the gas. If the flow is too high the expansion will cool it down so beware of frost bite

[@phizc]

I read on Wikipedia that the core can be cured in a microwave in just a few seconds, and if the form is transparent to microwaves (e.g. alumina, some or maybe most plastics), it can be cured in the form.
I haven't tried though. I'm still in the research phase (watching YT videos). 😅

[@rickhalverson2252]

CO2 is heavier than air... maybe it would be better to stand the bag up? The co2 stays on the part, air rises.

[@OgmiosForge]

Makes sense to me!

[@ctpctp]

But what percentage Sodium Silicate is your solution there?

[@TalRohan]

there is a recipe on here somewhere if you look up water glass recipe is 500mls water 300g of silica gel and 200g of sodium hydroxide (do it outside though because the fumes are caustic)