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Very interesting sand molding method.

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airmodel:

--- Quote ---question is, how many times before I give up?
--- End quote ---
I had the same thoughts. I remember when I purchased for the first time sodium silicate because I was having trouble using green sand. The foundry supplier said to me that any fool could use sodium silicate to make a mold and it was a replacement for green sand and skilled molders. About 3 years later I started to use green sand again and I would never go back to using sodium silicate. Complex statues of humans and animals were made with green sand before lost wax was developed.

airmodel:

--- Quote ---You also want to pick a cup with a mostly cylindrical handle hole, beefy squarish handle
--- End quote ---

I think the most difficult part is making a green sand core with prints and removing that core without breaking and then replacing it back into the mold.

He makes it look easy but I know from experience green sand cores can be a problem.

vtsteam:
@airmodel, maybe you could use some of those semi-circular shaped needles -- or a wire equivalent -- to pin the handle core without digging away some of the sand?

I also don't get exactly how he held it there while fastening, and keept it intact. It must have been very strong sand.

Tweezers have to extend down past the marble midline so will damage the bottom of the core there. Will need repair.

Big question... do you think the final product had some grinding/clean-up on it?

I'm keeping my eye out for a cup somewhat like that one....

vtsteam:

--- Quote from: airmodel on December 10, 2025, 11:56:42 PM ---
--- Quote ---You also want to pick a cup with a mostly cylindrical handle hole, beefy squarish handle
--- End quote ---

I think the most difficult part is making a green sand core with prints and removing that core without breaking and then replacing it back into the mold.

He makes it look easy but I know from experience green sand cores can be a problem.

--- End quote ---

Prints? The handle core is just flat to the edges of the handle, I thought. So free-standing -- which is why it had to be pinned in place.

petertha:
I'm not into casting (unless you include YouTube grazing, in which case I'm practically Yoda level haha). I'd like to one day, but it seems to be a whole hobby & specialized equipment setup unto itself. But I have a naïve, novice question after watching videos like RotarySMP casting aluminum parts for his Redrup radial replica. He uses 3DP parts to make patterns, but many of the casting molds are 'plain' sand with water glass (sodium silicate) mixed, tamped around the pattern & cured by CO2 gas. Aside from all the common trials & tribulations specific to preparing the aluminum melt, temp, ingredients, mold design... the resultant parts look pretty darn nice. Many castings with more complex internal shapes requiring cores. Why isn't this method a lot more popular with model engineers vs Petrobond or shop made oil/sand/clay recipes & the muller & recycling the more valuable sand? It would seem to me like a no brainer to buy very inexpensive clean sand, the goop, CO2 gas from any weld shop & you are off to the races. Maybe even finer sand mesh from ceramic supply shops for better detail. Yes, the spent molds become waste products, no recycling of material. OTOH essentially low strength 'rocks' wherever one can safely toss them. What am I missing, surely something?

https://www.youtube.com/@RotarySMP

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