(Sufficient to make 30 to 50 Kgs of core moulding sand dependant upon the addition rate)
Measure the amount of dry sand by pouring it into the core box or moulding boxes plus say an extra 10%. Weigh it in Kgs then work out 3% of the total weight (Example 2kg of sand = 2000gms 2000/100x3 =60grams this equates to 30grams per kilo of sand)
Sodium silicate is mixed with silica sand at proportions indicated. Mix thoroughly and ensure all sand grains are coated
Ram the mixed sand into the core box or mould and vent to the center with a 2mm diameter spike. This is to allow Co2 gas to be passed through the sand. The sand will solidify after 5 to 20 seconds by chemical reaction
The solidified core can then be removed and used in a greensand mould or full silica sand mould
I tend to use the 3% silicate mix. To make it easier for myself 1Kg of sand equates to 800ml and 30gms of Silicate equates to 20ml. I find it easier to use a large measuring jug for this.
Silica sand (washed dried and sieved) can be purchased from most builders merchants
The mixed sand can be kept for use in the future if it is stored in an airtight bag or container.
Large cores or full moulding boxes will require multiple venting and gassing
Co2 gas from a soda stream bottle is ideal or a brewery gas bottle.
After casting the core sand can be removed by softening with water once cooled off.
Thin or fine cores should have core wire to give additional support
Addition Rate 3 - 5% by weight depending on application type and foundry conditions.
Technical data sheet available.