$9.36
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Please note the "instructions" are in this description.
This is officially called "Tuf-stone" by USG, the manufacturer. Unofficially, this might be called 'fibrous Hydrostone' because of the similarities to standard Hydrostone. The water usage specification is the same as hydrostone and it has similar handling characteristics. The usage is 100 Tufstone per 32 parts by weight of water. The intended purpose for Tufstone is solid cast interior giftware, to compete with ceramic giftware. This gypsum cement evens the playing field since ordinary casting plasters have less chip resistance. USG says Tufstone has 3 times the impact resistance (impact results in chipping) as standard plasters. This is due to the fiber reinforcement along with the addition of an acrylic copolymer. USG notes that maximum chip resistance is achieved by power mixing. You can tell that the "fibrous" name is true because of the visible, short fibers that you can see when thin splashes of the cement are hardened and broken. There is a fuzzy protrusion of tiny fibers at the edge of the break My speculation is that they are the same common polyethylene or polypropylene microfiber we sell separately. I don't think they're glass fiber.
Ordinary molding/casting plaster, high strength pottery plaster, and even many gypsum cements have less resistance to chipping than low to mid fire ceramics (which have a reputation of their own for edges prone to chipping). This gypsum cement evens the playing field since ordinary casting plasters have much less chip resistance. Having said that, however, does not mean it has higher compressive strength than other gypsum cements (it has the same as Hydrostone) or any other significant strengths. It can be said to have more 'resiliency', but numerically, the 'modulus of resilience' increase is not provided because it's probably not significant. Both low fire ceramic and gypsum cements are generally low resilience materials (thesaurus synonyms includes 'elasticity' for 'resilience'). USG accomplishes this increase in resiliency (or impact strength) by the addition of fine, elastic fibers and a measure of polymer. Polymer addition (usually acrylic) is quite common in cements, including Portland.
Gypsum cements are wonderful for making castings. The process, I mean. The materials are benign, water and cement powder. The only hazard is chronic breathing of airborne powder if not wearing a dust mask. You can minimize that by making slower movements when dispensing the powder reducing airborne powder and wearing a simple mask.
Making castings with resin, any liquid kind, is not a wonderful process. Every kind of liquid resin has its advantages and disadvantages. Epoxy is popular right now, but a hidden danger that many don't take seriously is sensitization, first skin sensitization, then progression to more serious sensitizing (airborne parts per thousand or even million with serious cases). A large majority of people won't be in danger of sensitization but I mention it because I worked with an artist who progressed to serious sensitization over a period of 4 or so years. But even if you eliminate sensitization from the equation, resins and solvents are stinky and sticky. You have to wear protective gear, gloves mainly, but you'd better wear eye protection and more expensive masks for organic vapors. You will inevitably be forced to keep expensive flammable solvents no matter how neatly you try to avoid drips, spills, and stains. You will need even higher personal protection and ventilation for solvents. Yes, if you are only using small jewelry making quantities, then the inconvenience and danger goes down a lot. But, you will still be subject to sensitization if you work with epoxy, the best liquid resin in town right now (the artist I mention used jewelry sized portions).
If you compare gypsum cement and epoxy resin (epoxy being the most common, but there are others), here's how it stacks up, with Hydrostone as an example (our Tufstone hadn't arrived yet when that was written. If we redid the comparison using Tufstone instead of Hydrostone, it probably would have affected only #1, the other points would stay the same).
Using a roughly 40 mm (~1.5") diameter disc, about 3 mm (1/8") thick:
1) Resin could be broken but it would take some effort depending on resin.
Hydrostone could be snapped in two a little more easily.
2) Resin can be warmed & then bent & held until cool, it will remain bent.
Hydrostone would not be affected by temp. It would still break if bent.
3) Resin can be any pigment color either transparent or opaque.
Hydrostone is white and very opaque & can be lightly tinted by pigments.
4) Resin is expensive.
Hydrostone is cheap, perhaps 1/4 the price of resin (guesstimate).
5) Resin cannot easily be stained w/dyes after casting (it takes some strong solvents). "Stains" can be added as dyes and mixed in with the liquid resin before casting.
Hydrostone can be stained any color dependent on the casting's porosity.
6) Resin can be polished or will take the sheen of the mold it's cast in.
Hydrostone will also take the sheen of the mold.
7) Resin will not absorb water when fully cured.
Hydrostone will absorb water & needs to be sealed to prevent it.
8) Resin is lighter & will sound dull when dropped on a hard surface.
Hydrostone if optimally mixed is heavier & will sound more like ceramic.
9) Resin can be made hard or soft or scratchable.
Hydrostone if optimally mixed can be harder than resin.
10) Resin degrades silicone molds. A limited amount of castings can be made.
Hydrostone does not appreciably affect silicone molds. Many castings can be made (this point depends on the type of silicone and the type of resin used).
So, all in all, resin is a much more versatile material, but point #4, the lower cost of gypsum cement, perhaps overrides all the other points. It could be said that if a casting needs to have a certain color or transparency, resin would take the prize and you'd swallow the extra cost, inconvenience, and disadvantages. There are gypsum cements stronger than Hydrostone, but also more expensive and hard to find in single bags (Hydrostone Super-X is one).
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Aug 27, 2022
Excellent seller! Knowledgeable, and quick to respond to all questions. Thanks so much!
Lu LG