Measuring by Weight
Accu-Cast's general alginate mixing instructions call for a 4:1 (water weight to powder weight) mixing ratio. This is great for "Bucket Molds":
- 4 oz. alginate to 1 pound water (~1 pint)
- 1 pound alginate to 4 pounds water (~2 quarts)
- 2 pounds alginate to 8 pounds water (~1 gallon)
For "Layup Molds" like faces, heads, torsos, etc. some people prefer a "thick mix" of 3.75:1 by weight:
- 4 oz. alginate to 15 ounces water (15 fl.oz)
- 1 pound alginate to 3.75 pounds water (~3.75 pints)
- 2 pounds alginate to 7.5 pounds water (~3.75 quarts)
If you need help calculating how much alginate you will need for your project, this PAGE will help.
The reason we don't recommend measuring out your alginate by "volume" is that alginate is a "compressible powder". This means that alginate can be at a wide range of densities at any one time. In fact, fully compressed alginate weighs almost 40% more than fully fluffed alginate.
Measuring by Volume
If you MUST measure alginate by volume, use 5 parts water to 4 parts water. This is a decent pproximation. Remember this is for volumetric measurements only and will not be as accurate as if you were to weigh out both the water and the powder.
A Word About Your Water
Water is water- Right? Not Necessarily.
Alginate is a combination of chemicals each included in the formula to do a certain thing. If your tap water has just a little of one or more chemicals (phosphates, chlorine, salts, calcium, etc.) then you could get "less than ideal" results. Problems take the form of lumpy mixing, long or short setting time and poor quality of the finished casting.
To ensure that you will get optimal results, please consider using inexpensive bottled water to mix with your alginate. Doesn't have to be Evian, just store bought "spring water" should be sufficient.
If you have questions, contact us.