Subject: Impression Materials Manufacture & Pricing
To the lifecasting community,
I have noticed some discussion of lifecast materials and their relative costs. As both a lifecast artist and a manufacturer of certain mediums I thought some explanation of how pricing is established might be useful.
This is purely enlightened self-interest; the more you know the better my products look.
The first thing we have to acknowledge is that we can only rationally compare things of similar magnitude (i.e.; apples to apples). In the case of the so-called 'alginates', they are definitely NOT all created equal. Please bear with me a moment.
These chemical compounds all began as 'dental impression materials' under patents issued in the 1st half of the 20th century. The actual chemical compound called 'algin' or 'alginic acid' is the coating on certain types of brown seaweed and forms only a very small portion of the actual lifecast medium, typically in combination with sodium but potassium, calcium and other metals are also used. Its largest applications are in the food industry (i.e.; for coating onion rings, puddings & pie fillings, etc.).
By itself 'algin' does nothing but absorb phenomenal quantities of water (isn't nature wonderful?). Only in combination with several other chemicals does it form the highly detailed, flexible solids we all know and love. That chemical process is called synergy (the whole is greater than the sum of its parts) and is poorly understood scientifically.
Sodium alginate is by far the single most expensive part of the compound lifecasters call 'alginates'. As any experienced lifecaster knows, standard 'dental impression material' is far weaker than the 'prosthetic grade' versions. What's the difference? Primarily the concentration of this expensive sodium alginate in relation to the other, much cheaper components (this is a simplification).
As used in lifecasting the largest component by far is the water we add to form fluids which can then be applied to the body. Standard dental impression material can be made to perform as well as prosthetic grade if you simply add less water. Doing that of course gives us less overall volume of working medium, thereby raising the cost per unit of measure (i.e.; quarts, liters, etc.).
This also creates other complications, such as a faster setting time which I won't go into here. The point is that the entire subject is about ratios; how much of one thing in relation to another. Which returns us to the subject of price.
One impression material that contains only 3% of sodium alginate, for example can be sold for much less than one which contains 6%, all other things being equal. The difference is obvious when used by an experienced lifecaster. When mixed with equal amounts of water, one will be much thinner and weaker than the other. The cheaper one will not hold up as well in the matrix (mother mold), it will not capture as great a detail, it will shrink and crack faster, it will ooze water out faster (this is called syneresis) and not produce as high a quality castings nor as many from a single mold.
In other words, you get what you pay for.
Having said that, not all manufacturers have the same overhead burdens. Some can offer mediums with high algin concentrations at the same price as others with low concentrations. We all jealously guard our formulations but the only thing that matters to me, as a lifecaster is the material's performance.
Check around, do the math, try different brands. To be fair to all manufacturers you simply cannot lump all impression materials into the 'alginates' category and compare simply by price per pound. Your conclusions will be very incorrect.
- Mark S. Winn
- MSW Creative Works
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