Mixing Investment - Lacy West Jewellery Tools and Supplies

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Technical Information Sheet
Investment Mixing Procedure and Mixing Ratios

Investment Mixing Procedure
The investment powder is mixed with water, and the mixture is called a slurry. The proportion of water to investment powder must be controlled accurately to obtain uniform and perfect castings. Too much water will result in a weak investment mold. Too much investment will make the investment too coarse and important details in the wax pattern will be lost.

Room temperature, 70ºF, should be used during the investment procedure. The investment is added slowly to the water and mixed until the batch is uniformly smooth. Craftspersons can mix with a spoon or a hand mixer. The mixing time should be from 2 to 4 minutes to obtain a smooth batch of slurry.

Tools and Materials for Mixing Investment

Investment
Rubber Mixing Bowls
Casting Flasks
Sprue Bases
Vaccum Machine

Calculate the Amount of Slurry Required for a Casting

Volume of a Round Flask in Cubic Inches

= 0.07854 x diameter (in inches) x diameter (in inches) x height (in inches)

Volume of a Square Flask in Cubic Inches

= width (in inches) x length (in inches) x height (in inches)
Water-Investment Ratio for a Regular Casting
The investment is mixed with water by weight in the following proportions for a regular casting:

40 parts of water to 100 parts of investment
or
6-1/2 ounces of water to 1 pound of investment

Recommended Proportions for Regular Casting (40/100)

Investment Weight	Water Volume (cc)	Water Weight (oz)	Approximate Yield (cubic inches)
1 lb	182	6.4	21.9
5 lb	908	32	110
10 lb	1816	64	219
15 lb	2724	96	328
20 lb	3632	128	438
25 lb	4540	160	548

Water-Investment Ratio for an Extra-Fine Casting
For very fine, intricate castings, slightly more water (up to 2%) can be added to the investment to obtain a finer slurry that would flow easily into the small crevices of a detailed wax model.

Recommended Proportions for Extra-Fine Casting (42/100)

Investment Weight	Water Volume (cc)	Water Weight (oz)	Approximate Yield (cubic inches)
1 lb	191	6.72	22.5
5 lb	953	33.6	112
10 lb	1907	67.2	225
15 lb	2860	100.8	338
20 lb	3814	134.4	450
25 lb	4767	168	562

Water-Investment Ratio for a Heavy Casting
For heavy castings, slightly less water (up to 2%) can be used to obtain a slightly less fluid slurry that would be sturdier for heavier castings.

Recommended Proportions for Heavy Casting (38/100)

Investment Weight	Water Volume (cc)	Water Weight (oz)	Approximate Yield (cubic inches)
1 lb	173	6	21.3
5 lb	862	30.4	106
10 lb	1725	60.8	213
15 lb	2588	91.2	320
20 lb	3450	121.6	426
25 lb	4312	152	532

The Lost Wax Casting Process

Rendering a Jewellery Piece
Making a Wax Model
Mixing Investment
Burnout Cycle
Casting a Piece of Jewellery
Making a Rubber Mold
Making Wax Copies from a Rubber Mold
Casting Pieces of Jewellery

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