Anti-Porosity Aid for Hobbyist Bronze Casting

Hobbyist bronze casters, like the one in the Reddit post "Why these bubbles," often struggle with persistent bubbles on the bottom of their ingots. These issues can be really frustrating, especially when common fixes like preheating the mold don't seem to help.

Product Suggestions:

  1. Bronze Degassing Agent for Hobbyists: An easy-to-use, pre-portioned degassing agent (like pellets or powder) specifically designed for common bronze alloys and typical hobbyist melt sizes (1-5 kg). The packaging should include clear, simple instructions for safely adding it to the melt to remove dissolved gases.

  2. Anti-Porosity Mold Coating for Bronze: A ready-to-use mold wash (either brush-on or spray-on) for common hobbyist mold materials like graphite, investment, and sand. This coating would create a smooth, non-reactive barrier to improve metal flow, prevent reactions that can generate gas, and help any trapped air or gases escape, especially from the bottom of the mold.

Expected Benefits:

These products could significantly reduce casting defects like bubbles and porosity for hobbyist bronze casters. This would result in higher quality and more consistent ingots and finished pieces, less wasted metal and fuel, and more satisfying and successful casting experiences.

Origin Reddit Post

r/metalworking

Why these bubbles

Posted by u/Fabulous_Item_963906/04/2025
I’ve tried to cast this bronze several times but it always ends up with these bubbles on the bottom of the Ingot. Why is this happening and what can I do to fix this. The mix is around 70% co

Top Comments

u/Onemilliondown
You need to pre-heat your mold to remove any moisture before you pour. Also, there are possibly impurities in the brass.
u/Fabulous_Item_9639
I usually skim it off the surface of the metal before pouring, but yeah I used borax.
u/Fabulous_Item_9639
I set the mold onto the foundry before casting g for that very reason, it got red hot before I cast it. Maybe impurities, what would I do in that case?
u/Normal_Imagination_3
I'm not very knowledgeable on casting but would pour speed be a possibility? If you pour it slower it might help the air bubbles not form
u/Fabulous_Item_9639
I set the mold onto the foundry before casting g for that very reason, it got red hot before I cast it. Maybe impurities, what would I do in that case?
u/Normal_Imagination_3
I'm not very knowledgeable on casting but would pour speed be a possibility? If you pour it slower it might help the air bubbles not form
u/bodatbgst
Im not smart enough, but do you pour enough borax when you melt the brass?? Cmiiw🙏🏼
u/Onemilliondown
You need to pre-heat your mold to remove any moisture before you pour. Also, there are possibly impurities in the brass.
u/bodatbgst
Im not smart enough, but do you pour enough borax when you melt the brass?? Cmiiw🙏🏼

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