Now, you can increase the size of your original without distortion and with controlled expansion!! Expandit is a positive casting medium that you can use with any sealed or non-porous mold
Instructions for EXPANDIT:
. 10-minutes working time
. One-and-one-half-hours demold time
. Mix ratio: 100 parts “A” to 50 parts “B” (by weight); or 100 parts “A” to 54 parts “B” (by volume)
Since Expandit is a urethane product, if you use a silicone mold, no release is necessary. We strongly recommend that you do not use a urethane mold to avoid the risk of adhesion. If, however, you have no choice but to use a urethane mold, you must first apply a wax or silicone spray release to the mold; otherwise, your Expandit cast will stick to it. Plaster molds must be sealed, and then a release applied over that. For instance, if you seal your mold with shellac, you will need to apply a separator (paste or spray wax) over that, or else the Expandit will stick to the shellac.
Do not use an electric mixer or drill, as this will introduce too many air-bubbles to the mix. Stir with a spatula; and then pour into a second container, so that what was on the bottom of the first container is now on top. Stir again with a spatula, then pour immediately. Remember that you have only about ten minutes of working time.
Expandit will not work in an alginate mold because the moisture immediately reacts with it, causing a separation between the surface of the Expandit material (that is in contact with the alginate) and the rest of the Expandit.. The mold you use must therefore be moisture-free.
After de-molding, immerse casting in water and leave it there until it achieves the desired size. It is important to wait at least 4 hours after removing your casting from the mold before you immerse it in water. Initially, a bumpy texture may rise on the surface as it expands; however, this texture will eventually level-out as the form contiues to soak and reaches its fully expanded state. As the bumps disappear, the casting will retain most of its fine detail…even fingerprint detail! Bumpiness may occur as a result of “hard” water or if the casting has not been allowed to”rest” for four hours after removal from the mold, to allow the material to stabilize before immersing it in water. The maximum expansion is approximately double in size. The duration of the expansion process will vary, depending upon the size of the casting. It can take anywhere from a few hours (for tiny pieces) to a few days (or a couple of weeks for larger pieces) to achieve maximum expansion; so you must carefully monitor the process if you want a precise size. If you remove the casting from the water, it will slowly reduce back to the original size. After having removed the casting from the water, if you want it to shrink back down somewhat, you can allow it to air dry. This property can be helpful if you have accidentally allowed your piece to expand more than you had wished. As the casting shrinks, the bumpiness will not reoccur on the casting as it did in the expansion process. Once you begin your permanent mold of the expanded casting, it will quickly be sealed-off by your molding rubber, so it will not tend to shrink from its expanded state.
To make your permanent mold from your expanded casting, we recommend that you use a fast-setting silicone. You cannot use a slower silcone to make your mold because the moisture from the Expandit casting will inhibit the cure of a slower silicone. A fast-setting silicone is one that fully cures within half-an-hour. Our Silicone-10 gels within about 5-minutes, and is fully cured in about twenty-five minutes.
Expandit becomes increasingly fragile as it expands; so, if you are not very careful, just in the process of removing it from the water, it can tear or crack; because it becomes gelatin-like. If it does tear ever so slightly anywhere, this tear will dramatically increase as the moisture leaves it, because of the increased surface tension. The degree of stress caused by surface tension during expansion or shrinking will vary tremendously from one form to another because it is a matter of the relationship of adjacent volumes. It is therefore crucial to avoid even minor tearing while removing the form from the water bath. If you see even some minor splitting occurring during expansion, you must remove the casting immediately, because it will only get much worse.
Some distortions may occur, depending upon the thickness of the object and how many times you enlarge it. You can only control the rate of expansion by carefully monitoring your casting as it expands. However, you have to bear in mind that thinner areas will expand more quickly than thicker areas (because they will absorb water more quickly); so, you may have a situation where you will want to keep it in water longer so that the thicker areas “catch-up” to the thinner expanded areas. The only way to get an even thickness (and even expansion) throughout your casting is to begin by hollow-casting your piece with a core inside. So, your “wall” between the core and the inside of the mold is more or less an even thickness everywhere; and you want to keep that thickness to about one-half to three-quarters of an inch. If you have thin areas and thicker areas in your casting, there is a much greater chance of the form splitting as it expands (again, due to surface tension). Areas thicker than 3/4 inch can possibly crack or split if left in the water too long (but won’t necessarily do so); and this is why we recommend the core approach to thicker projects. Because you are then working with a hollow casting, you have to support the interior very carefully before making your mold of the expanded form.
Part A of EXPANDIT has a very limited shelf-life. Please use the material within one week of delivery. The more air in the container, the shorter its useable life-span. Always store Part A in a cool place to prevent crystallization. If you use 20% or more of the material, it is always best if you transfer the remainder into a smaller container so that there is less air between the lid and the top of Part A; otherwise, it will tend to gel or crystallize in a matter of just a week or two. If your containers are well-sealed, with very little air between Part A and the lid of the container, it could last longer.
NOTE: Do not attempt to cast forms thicker than one inch; otherwise, you may experience serious cracking and distortion. If the piece you are enlarging is more than two inches thick, you must hollow cast (with a core) in order to achieve a successful enlargement. If you need guidance with this, please telephone us for technical help! Please do not e-mail us with technical questions. Please understand that we do not have the time to answer even a one-line question, which may require a full page of written explanation.
SAFETY NOTE: Expandit is a urethane product. Skin contact with the raw materials should be avoided, so please wear protective gloves and work in a well-ventillated area.
EXPANDIT is $12. per pound……Minimum order is a three-pound kit ($36.)
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