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Fireclay (for molding sand)

The right amount for a 50 pound bag of sand

One of these packages of fireclay is the right amount to mix with a 50 pound bag of playsand (sold at the HomeDepot, lowes, etc.) making a very high quality molding sand (greensand). This is a lot less expensive than paying shipping on 50+ pounds of ready-mixed molding sand!

Learn to mix the molding sand further down on this page.

A package of firelay Fireclay package
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Mixing molding sand (greensand)

How to easily mix your own reusable casting sand

Sand casting metal involves pouring molten metal into molds made of a sand/clay mixture called "greensand." Here are instructions for mixing your own greensand which can be reused hundreds of times.

Playsand poured in a tub

Begin by pouring a 50 pound bag of playsand into a large mixing tub.

Playsand is an extreamly fine sand used in children's sandboxes. The finer the sand the smoother the surface of the castings will be. This sand is so fine it almost feels like a powder.

I buy mine from the Home Depot store and in some cases it is packaged with the name "natural sand" instead of "playsand" on the package.

Fireclay ready to be added

Make sure the sand is moistened slightly (it is usually sold moist already). Have the fireclay ready since it will be added next.

Fireclay added to the sand

Spread the clay (it is in powder form) over the sand and mix it in thoroughly.

It is good to pour in half the clay, mix it around and then pour in the remainder of the clay and mix thoroughly.

The finished molding sand

Here's the molding sand fully mixed and ready for use. It's a very simple process. It is best to let it set for an hour before use so the clay can fully absorb the water and bond to the sand better. The sand tends to improve after a few usages since the clay get a further mixing-in.

Specialty molding sands exist with other ingredients mixed in, but that is beyond the scope of this introduction.

Question: How many times can the molding sand be used?
Answer: The molding sand can be reused HUNDREDS of times. After pouring metal into it, the hard clumps of dried sand are simply re-tempered (sprinkled with water to bring it back to the proper moister content) and broken apart. So depending on how often you cast metal it can last for many years. Usually you know the sand needs replacing when it stops sticking together well and falls apart in the molds. This can be a result of the clay bonding being "worn out" or the eventual buildup of the parting compound dusted onto the sand during the mold making process. For more details of various sandmolding processes get yourself a copy of How to cast metal in sand.

The sand squeeze test

Testing the sand

A good test for the sand is to squeeze some in your hand. The sand should compress together firmly and show good detail of your hand. Very little sand should stick to your hand.

If the sand does not squeeze together well and crumbles it is too dry, add more water. If it is "muddy" and sticks to your hands a lot it is too wet, let it dry out some. Give the sand at least an hour after mixing before you test it so the clay can fully absorb the moisture.

clumps of molding sand

The squeezed sand should break apart in large clumps with very little crumbling. The moisture content of the sand should be like a well rung out sponge. I once read it described as being like "brown sugar" but not as sticky, which is a good comparison.

Open mold

A mold made in an 8" x 8" flask shown open for illustration, before pouring the metal.

Question: How many molds can I make at a time with 50 pounds of greensand?
Answer: Depending on the size of your patterns (larger patterns fill more space in a flask requiring less sand), this batch of molding sand will fill on average, two 8" x 8" flasks and one additional smaller flask.

Open mold

After opening the poured mold the casting is visible. A 7" long boat anchor paperweight!

Bucket of sand

The sand fits conveniently into a 5 U.S. gallon plastic bucket for storage. Keep the sand covered so it stays moist and to keep debris out.

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$34.95 total
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