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| Casting |
How do I avoid air bubbles in my part?
Cast Alumilite into a warm mold coated with baby powder. This will help the material flow better and cure more evenly. If you are using silicone rubber, stick the mold in an oven set at “Warm” for approximately 30 minutes or put your mold in a microwave on high for 1 minute per lb of rubber. Once your mold is warm to the touch, sprinkle baby powder or talc powder in the mold. Shake the powder around the mold so all areas are covered. Once covered, knock or blow out all of the excess powder. This will leave a light coat of powder on the outside of the mold that will release the surface tension and allow the material to flow much better reducing the chance of trapping air bubbles. You can also use any kind of paint or commercial brand of urethane release to aid in the problem if baby powder isn’t available. For complex molds that have severe undercuts, you may need to vent those troubled areas with holes that can be created with either some copper tubing or an Excel or Exacto knife. |
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What is the best way to pour my part to eliminate air bubbles that are formed when casting?
If you are casting a part in an open or one piece mold, pour slowly from one corner of the mold and let the material flow naturally to fill the mold. If it is possible run the material down one side of the mold. If the mold has an undercut or complex corner you may pour the material to that point and then rotate your mold to evenly coat that area before topping off the mold. If you are pouring a closed or two piece mold, fill it completely until the material comes out of the vent hole and then tap the mold on the table to release any bubbles that may need a little assistance to get through the vent hole. You may also wish to rotate the mold and possibly squeeze the sides of the mold to assist hesitant bubbles in reaching the vent. |
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Can you vary ratios?
No. Varying the ratios will not affect the working time but it will affect the cure time and physical properties. Meaning, Alumilite will still start to set up in it's normal time but could take hours to completely cure. When it finally does cure, it will not have the same properties of the regular resin and may be considerably weaker. |
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How much heat does Alumilite generate?
This depends on the mass you are pouring, but typically ranges between 120°F to 200°F. |
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Can the set time be increased?
Yes! To get an additional 30 - 60 seconds, cool the "B" side of Alumilite in the refrigerator for 3-5 hours. When you cool the resin it is important to remember to pour into a warm mold for proper curing. |
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What is the difference between Alumilite Regular and Alumilite White?
Alumilite Regular is higher in strength than Alumilite White. Alumilite White is the thinnest resin Alumilite manufactures and is the easiest to use. It is also slightly softer and was created to pick up the absolute best cosmetic reproductions. Both are highly machinable and can be painted, drilled, tapped and sanded. |
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Can Alumilite be colored? What do I use?
Yes. Alumilite offers a full line of dyes specially formulated for Alumilite’s Casting Plastics. If you use an outside source make sure that the dyes/pigments are not water based. Some oil-based dyes are compatible. Test a small amount before mixing in larger quantities. Most powdered dyes will work if they do not contain any moisture (known as a dry filler). We also have a line of metallic powders that you may use in your molds to color Alumilite. |
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Are all of Alumilite’s resins UV Stable?
No. The only naturally UV stable resin is Alumilite’s Water Clear. Alumilite opaque resins will yellow over time if it is exposed to UV light. Clear acrylics or lacquers work well for protecting the resins from changing color. There are two ways of applying paint to achieve the best adhesion. First paint the mold and allow it to completely dry before casting your resin. As the resin flows into the painted mold, it will chemically bond to the paint as the resin is curing and after the resin cures you will demold a perfectly painted part. Painting the mold prior to casting allows you to reproduce perfect detail by painting becoming the outside layer of the actual part rather than cover the exact cast replica with paint that could then cover up fine detail. The other option for painting your part is to paint the part as soon as you remove the cast part from the mold and after you remove any flash while the resin is still curing. Although the resin is demoldable, the casting resin is still curing and if painted during the first 5 or 10 minutes of casting the part, the resin will still crosslink with the paint to give you not only a mechanical bond but also a chemical bond between the paint and the cast piece. Paints have built in UV stabilizers which then block out the UV light from ever reaching the casting resin which could affect the color. |
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How long should I mix Alumilite?
Mix thoroughly for 20-30 seconds (be sure to scrape the sides and the bottom of your container). It should be mixed until absolutely no swirls or striations are visible. Try not to mix the resin in the graduated measuring cups because the raised letters and rigid inside prohibits you from scraping the sides effectively. |
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How much heat can Alumilite take before deforming or melting?
Alumilite will not melt. It will start softening in the mid 200°F and discoloring above 450°F. The shape and design have a lot to do with the physical resistance to heat. If there is no load on the part itself, it may soften at elevated temperatures but with no deform. However if excessive pressure or a load is applied, the resin may start to deform at lower temperatures. |
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Can I paint Alumilite?
Yes! We recommend lacquers or acrylics but you may also use synthetics or enamels. A lacquer primer may be needed to assure the long tem effectiveness of the paint. You may wish to paint your silicone mold before casting Alumilite. Paint the mold with a fast drying acrylic or clear coat. Once it is completely dry, cast your piece. When you demold the part you will pull out a painted piece. Alumilite will chemically bond to the dried paint. The other option is to paint the part as soon as it comes out of the mold while the resin is still curing to allow the curing resin to crosslink with the paint. |
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Can I spin cast Alumilite?
Yes! Alumilite works extremely well in a spin casting machine. Although spin casting was originated for low melt metals, you can get excellent castings with Alumilite. This technique allows you to produce many parts in a fraction of the time of conventional pouring and provides users a very effective means of casting perfect parts. |
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Can I rotational mold Alumilite?
Yes! Alumilite’s low viscosity is ideal for picking up the detail required in thin walled rotational molded pieces. The hollow center will cut cost dramatically by reducing the amount of material that is required to cast your part. (Call us for detail on Rotational Molding Equipment.) Sometimes it is helpful to use microballoons to fill the resin to increase the consistency/viscosity to allow for thicker coats to be rotated at one time. |
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What kind of mold release can I use?
If casting into a silicone rubber mold, it is usually not necessary to use a mold release because of it's natural no-stick tendencies. If in doubt, Alumilite offers a Stoner Urethane Mold Release that will not only help release your part but will also extend the life of your mold. If you are pouring into molds that are not made of silicone, a thick layer paste wax or Stoner is required. If you use a mold release, you may need to wash your parts prior to painting in order for the paint to stick. Alumilite’s UMR mold release is a dry film release used for separating silicone to silicone, urethane to urethane or urethanes from silicone. It is not as effective as a mold life extender as the Stoner but can be used between multiple materials as where the Stoner is used primarily for releasing urethanes from a mold. |
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Why is my Alumilite Casting resin foaming?
Moisture contamination in urethanes causes foaming. If it foams quite a bit, most likely the moisture is right in the Alumilite. The moisture is usually in the A-side. There is not a full proof method of removing moisture from your system. Typically the B side will crystallize when moisture is present. The A side, however, will not look any different. You can try to use a molecular sieve in the A side. Mix the sieve into the resin and allow to settle to the bottom for a couple days. Then test the resin to see if the sieve was effective in removing the air. You can also try to vacuum the A-side to relieve it of moisture. Vacuum the A side for 20-30 minutes until it completely stops bubbling. If you don’t have access to vacuuming equipment or a molecular sieve, the last chance would be to boil the moisture off. This is possible because water has a lower boiling temperature than any of the other liquids in the A-side. To boil off the material, we recommend that you put the Alumilite resin in a glass or metal container and place the material in an oven at 250°F for 2 hours. This will draw the moisture out of the system and evaporate it. If you are getting a bunch of little pinholes, the moisture is probably coming from some materials you are using (mold, cups, stir sticks, filler, etc.). |
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Is it necessary to vacuum or pressure the Water Clear and Flex 80?
Not in order for it to cure but yes in order for it to cure with absolutely no air bubbles present within the cast piece as well as the best physical properties. Both of these materials start out at a higher viscosity (thicker) than the other Alumilite resins. Therefore, when these two materials are mixed, the viscosity (consistency) of the material does not allow the air bubbles to freely find their way to the top of the cast piece as the other much thinner resins do before the material cures. These two materials feature a slightly longer open/work time in order for you to either vacuum and/or pressure cast to eliminate all of the bubbles within the casting. |
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| Molding |
What is the difference between the HS II and the HS III moldmaking rubber?
The only difference between the two rubbers is the hardness. The HS III is softer and more flexible making it a better choice for one piece molds that contain deep undercuts or negative drafts. The HS II has better dimensional stability and is better suited for less undercut one piece molds and for two piece molds due to the stiffer nature of the cured rubber allowing it to line up better with a second half of a two piece mold. |
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What types of molds can I pour Alumilite into?
With the proper release, you can cast Alumilite into almost anything. Here are a few examples: Silicone, Wax, Non-Sulfur Clay, Urethane, Latex, Plaster, Steel, Aluminum, and Wood. A thick paste wax or the Stoner Urethane Mold Release is required for non-silicone based items. If the mold is not made of silicone, the Alumilite resin is more than likely going to bond to it. So make sure the mold surface is not porous (cloth, wood, etc) and that you have an adequate layer of paste wax and/or Stoner on the mold surface. |
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What is catalyst?
The catalyst is what causes the RTV to cure or harden. It is either tin or platinum base. The tin base systems are much more user friendly and will harden against practically any surface. |
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What rubbers are compatible to pour over one another?
You can pour tin over tin base, platinum over platinum base and tin over platinum base. You can not pour platinum base over tin base as the tin will inhibit (not allow) the platinum to cure where it comes in contact with tin (mold surface). |
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How many parts will I get per mold before the mold starts to break down?
This all depends on the intricacy, what material you are pouring, and the detail of the part. Other factors are how many undercuts and how well the mold is cared for. It also depends on how often you are pouring, how hot your mold gets and if they are allowed to cool between pours. The following are estimates done with the use of a mold release using Alumilite resins.
J, M-2 ----------------------75-150
HS 111 ----------------------50-75
HS 11 ----------------------- 40-60
5 Minute Molding Putty --35-60
Quick-Set -------------------10-40
3110 -------------------------10-40 |
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Is there anything I can do to prolong the life of the mold?
Using mold release before pouring parts can double the life of your mold. You can also use/wipe Alumilite’s Silicone Oil on the mold surface before storing. Over time, the silicone oil will absorb into the silicone rubber mold to replenish some of the oil that has been lost during normal casting and demolding of your parts. The other option is to use a bake out process. A bake out process of the silicone rubber will help remove hardeners, plasticizers, and other materials that leach out of the casting resin materials that are on the molds surface. A slow gradual bake of 200 degrees F for 8 hours or 400 degrees F for 2 hours is recommended. This will also draw silicone oil within the rubber mold back to the surface to replenish what has been depleted. It is recommended to do this throughout the entire life of the mold rather than only when the mold dries out and is near the end of its life. |
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What is vacuuming and why should I do it?
Vacuuming: A vacuum pump is like a vacuum cleaner. A vacuum cleaner is designed to pick up things such as dirt off of carpet using suction or vacuum. A vacuum pump is identical to a vacuum cleaner, except it will have MUCH more suction. A vacuum system is measured in the amount of vacuum it will pull. In technical terms, it is measured in inches of mercury. A common household vacuum will pull 1-2 inches of mercury. A good vacuum pump will pull 29-30 inches of mercury. A vacuum pump is used to suck the air from the mixed silicone to assist in pouring air/void free molds. The concept is that when we mix the silicone we mix in tons and tons of air into the mix. Ideally, we want to remove the air from the mixed rubber so it doesn’t end up in our cured rubber mold and we’re really trying to avoid any air bubbles from sticking onto our original parts surface that would show up in our cured silicone rubber mold. When you put the mixed rubber that is full of tiny air bubbles under vacuum, it makes those air bubbles expand into big air bubbles which now have the buoyancy to float to the top and pop which removes them from your liquid rubber. If they remain small, they do not have the buoyancy required to float through the thick consistency of the rubber and get to the top. The thicker the rubber the harder it is for small bubbles to float and hence the need for the vacuuming rises.
Vacuuming Silicone: Our QuickSet Silicone has a thin enough viscosity the majority of air bubbles will rise to the surface without a vacuuming system. Dow Corning Silastic “J” & “M-2” are too thick to allow air bubbles to rise. Therefore, you must pull a vacuum to assure no air is entrapped. Once your vacuum reaches 29-30 inches of mercury, the rubber will foam up. You will need a container around 4 times the size of the amount of silicone you are mixing. Once the rubber has risen, it will break (meaning to fall quickly). After the silicone falls, you will want to keep it under vacuum for another 2-3 minutes. Then remove the material from the vacuum and pour the rubber over your master. You may want to pull a second vacuum after the mold has been poured. This will remove any air that you may have entrapped while pouring. Remember, once the rubber has risen and fallen, it will not rise again. Our Vacuum Chambers are 10” x 12”. |
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| Misc |
Is Alumilite safe or toxic?
Alumilite is non - toxic and virtually odorless. First of all, we recommend you read any and all MSDS (Material Safety Data Sheets) and warning labels on any product that you use. All urethanes contain some type of Isocyanate. We have a very small, diluted amount of MDI Isocyanate, which was deregulated as hazardous and is not considered to be a hazardous material. Alumilite resins contains no mercury, (other than Alumilite Clear). Alumilite is not considered to be carcinogenic. Alumilite is safe to use in your home but is not recommended for children without adult supervision. |
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What is the shelf life for Alumilite’s casting resins?
1 year, however as long as the resin has been kept free from moisture, it may still be good to use for much longer periods of time. Resin that has been as old as 4 and 5 years old works with no problems as long as it has been sealed and free from moisture. |
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What is the shelf life of Dow Corning’s silicone moldmaking rubbers?
Dow Corning warrants the silicone rubber for 6 months but similar to the urethane resins, moisture is the cause of problems and shelf life. So store your silicone rubber in a clean and dry place to maximize the shelf life. |
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Can I buy just one side of Alumilite or just catalyst for the rubber?
Yes. We typically stock extra catalyst for the silicone however if it is not in stock, expect a lead time of 5-10 days. |
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