In my earlier videos you will see I was using a baked core.
Here is the recipe:
Core making with Sodium Silicate
I am now using some core sand and sodium silicate from Artisan Foundry and they have given much better results than the pottery suppliers product previously used. The sodium silicate is thicker and has a light brown colour, the pottery suppliers was clear. The finished core is very smooth and no loose sand falls off. The finish is so good it could be used a mould instead of greensand.
Following the recommended ratio given on the bottle, I weigh out 500g of 60 grit silica sand, add 10ml of sodium silicate and mix using a paint stirrer in an electric drill.
This is then rammed into the core box with a removable wire in the centre to vent, and C02 gas passed through for up to 20 seconds.
The core hardens by chemical reaction and can be removed from the core box and used immediately.
I am using a bottle of gas sold as carbon dioxide welding gas .
Removing the Core
After casting the core sand can be removed by soaking in water once cooled off.