Frequently Asked Questions
Can I use Astro-Vest® investment to cast stones in place or for gold casting?
Although ASTRO-VEST investment will certainly create a mold strong enough for stone or gold casting, it will not protect the stones from heat damage. ASTRO-VEST investment is a much harder investment, especially when removing the investment from gold castings. Generally, a phosphate material is not recommended for gold or silver castings because the softer metals become distorted or damaged during the process of cleaning the investment from the casting.
Is 1400°F (760°C) the maximum temperature for ASTRO-VEST investment burnout? If not, what is?
Phosphate materials can withstand temperatures of 1800°F (982°C), but these temperatures are not normally required for most casting applications.
For what alloys do you recommend R&R® ADVANTAGE™ investment?
R&R ADVANTAGE investment is recommended for casters of silver, brass and bronze jewelry pieces.
What are the application differences between R&R ADVANTAGE investment and Ultra-Vest® investment?
Both products are prepared in an identical manner.
If I alter the amount of binder being added to the powder, will the mold strength be altered?
Yes. If you reduce the amount of binder in a mix, you will create a stronger mold. The mold will dry faster, but the working time will not be affected. Remember that a stronger mold is harder to clean from the castings.
What is the difference between R&R® Solitaire investment and other R&R gypsum investments?
R&R Solitaire investment is a gypsum-based material containing ingredients that protect the gemstones during the high temperatures of burnout and casting. R&R Solitaire investment has different characteristics than regular gypsum investment. Since stone-in-place castings are not normally quenched out of flasks after casting, R&R Solitaire investment is not designed to quench out easily.
Why does R&R Solitaire investment turn green when I mix it with water?
Coloring was added to the formulation as a safety measure. This allows you to confirm before casting that the proper investment is being used with stones. The color itself does not affect the performance of the investment or its measurable properties.
Can I steam dewax with R&R Solitaire investment too?
Yes. Simply follow the recommended burnout cycles.
I cast gold pieces, with and without stones cast in place. Can I use the R&R Solitaire investment for both types of castings?
R&R Solitaire investment does not have the same quenching characteristics that ULTRA-VEST investment has. Therefore, you will likely have a difficult time trying to quench flasks cast in R&R Solitaire investment. Some mechanical means of investment removal is recommended. However, both products are prepared in the same manner and R&R Solitaire investment can be elevated to the same burnout temperatures as the other investments if gemstones are not preset in the wax patterns.
What are your recommendations to remove R&R Solitaire investment from the tree?
Few casters quench flasks containing stones when hot because there is such a high potential for cracking the stones. Therefore, the product was formulated in a manner that does not respond well to quenching. After allowing the flask to cool for several hours at room temperature, you are advised to use a mechanical system, like a high pressure water blast or sand blasting, to clean the investment off the tree. Others prefer to soak the tree in a hydrofluoric acid solution. Proceed carefully in this procedure; the alloy and/or the stones may be affected by the solution. You may also want to set up a screen system to catch any loose stones that may be dislodged during the cleaning process.
What types of stones can be cast with R&R Solitaire investment?
Hard, small jewelry grade stones (.25 carat and smaller) make up the bulk of the stones being cast in place. Jewelry grade stones can be synthetic as well as natural, but they need to be hard enough to withstand the high temperatures experienced at burnout and casting. Be advised that industrial grade stones, which usually include defects and inclusions (hence, they cannot be rated as jewelry grade) are never recommended to be cast in place. The inclusions can allow oxygen into the stones, resulting in damage (burning) during a normal cast in place process.
For which alloys is ULTRA-VEST investment recommended?
ULTRA-VEST investment is recommended for gold, silver, brass and bronze jewelry casting. Similar alloys are appropriate for this investment, provided the melting temperature of the alloys remains below 2200°F (1200°C).
What is the highest flask temperature you would recommend for ULTRA-VEST investment?
ULTRA-VEST investment molds will stay stable up to 1400°F (760°C). Normally, you would not have a need to get the flask this hot. Once the mold has been cured and fired, reduce the oven temperature to the desired casting temperature. If you ever have to delay casting and your oven is filled with burned out molds, hold the molds at the desired casting temperature. If you cannot complete the casting, do not drop the temperature below 400°F (205°C). Cast as soon as possible.
What investment is recommended to cast white gold (palladium)?
Unlike other gold alloys, white gold (palladium) melts at a high temperature(2200°F or 1200°C). This temperature is also where gypsum materials start to decompose. You can cast in gypsum investment, but the process is sensitive to technique. You are advised to get both the metal and flasks as cool as possible to completely fill the mold and reduce the risk of the mold degrading. Keep the sprues thick and short. If mold temperature were the only consideration, you would select a phosphate material to cast white gold (palladium). However, the strength of the phosphate makes it difficult to remove the cast piece. We recommend Ultra-Vest® MAXX™ investment for white gold (palladium).
Is your investment hazardous?
Due to the presence of respirable particles (<10 microns) of crystalline silica in investments, these products do carry a respirable warning. It is extremely important to determine the level of exposure to which your operators are regularly subjected. The Safety Data Sheets (SDS) outline the personal protection guidelines for operators, based on the amount of exposure. Refer to the SDS for the product you are using and contact a health and safety expert with any questions you may have.
Are these control chemicals hazardous to your health?
Each control chemical is used in a very small quantity in the investment formulation. Regardless, none of them are hazardous to your health.
How long should I wait to quench out my gypsum molds?
Usually, quenching occurs shortly after the sprue button loses its red glow. If you quench too soon, you may alter the grain structure and create a rough surface. If you wait too long, the investment may be a little more difficult to remove and will quench less efficiently.
Are there any uses for the spent (used) investment? Can I grind the material and add it back into fresh material at some small ratio?
Although there are probably a number of practical uses for the spent investment, we cannot recommend anything other than disposal. After casting, the investment may carry traces of heavy metals that can limit other potential uses. Because the thermal properties of the investment have been permanently altered by the burnout cycle, the spent investment is very different from the new investment. Do not try to add the spent material into fresh material in any ratio. It will ruin the fresh investment.
Do investment molds shrink?
Yes, but the amount of shrink is very small, around 1%. Keep in mind that the wax, metal and investment all shrink during some part of the casting process.
Preparation & Investing FAQs
I have been advised to roll my investment drums and redistribute the powder before I use it. Is this required?
The particle size of the ingredients used in R&R investments are all of a similar (and very small) particle size. Therefore, there is no separation of the ingredients. You do not need to roll the package to redistribute materials. However, a few casters roll the package simply to decompress settled material, making it easier to scoop out.
You recommend vacuuming until the investment rises and breaks. You say this should take less than a minute. If it doesn't occur in a minute’s time, should I keep the vacuum applied until it does?
If the investment doesn't rise and break quickly during the investment cycle, there is usually a problem with the vacuum. Vacuum pumps with old oil or leaks can cause the vacuum to pull less vacuum than a well-maintained unit. An oil change often makes a significant difference. You can check the system by placing water under vacuum. If you do not see the water boil rapidly, you should get the vacuum system checked. If the water boils and your investment does not, contact your investment manufacturer.
Is distilled or deionized water required, rather than tap water? What is the difference?
Distilled or deionized water is recommended because it is more consistent than tap water. Impurities in tap water can change the working and set time of an investment. With distilled or deionized water, the impurities are minimized so the investment properties are more repeatable drum to drum and batch to batch. All of R&R’s retained batch samples are evaluated using deionized water to ensure batch to batch consistency.
At times, I would like to lengthen or shorten the set time of the material I am investing. Do you have any suggestions?
In general, warmer water and/or warmer powder will speed up the setting time. Cold water and/or powder has the opposite effect.
Does a flask really have to set undisturbed for an hour or two before removing the sprue base? I would like to speed up my production cycle and remove the base sooner than an hour.
The investment does require at least an hour’s time to set completely. Many customers see finning and other defects associated with removing the sprue base too early. If the base is removed before the investment has sufficient green strength, the investment is shifted and stressed when the base is removed. This can result in rough surfaces and other casting defects.
Is there any easy way to increase the strength of a mold without compromising quality?
Reducing the amount of water used will increase mold strength. Rather than using a 40/100 ratio for a gypsum investment, you may want to try 38/100. However, the increased mold strength will reduce the ability to remove investment after casting. The permeability of the mold will be reduced when less water is used.
Can I add water to the powder?
This method of mixing is not advised since it takes too long to completely wet out the powder. The material has a set working time and it is important to keep the mix time (3 minutes or less for a gypsum investment) as recommended so there is enough time to compete the entire process. Adding the powder to the water will allow you to mix thoroughly in the desired time.
Even though I think I have good vacuum, I still get nodules on my castings caused by excess air on the wax. Do you have any advice?
Often, altitude will reduce the effectiveness of even a good vacuum system. One of the tricks you might try is to add a few drops of liquid dish soap to the water before you mix your investment. The soap will act as a surfactant and break up the air bubbles in the mix. Be careful not to add too much soap or you could cause the opposite effect and create more bubbles.
Do I need to use the entire recommended working time for your investment like other manufacturers recommend?
Other manufacturers may advise using the entire working time as a means of eliminating water marking defects. Water marking is characterized as “rivers” of metal on the underside (as invested) of the casting. It is caused by water separating from the investment as it sets. Use of the entire working time is not a requirement to achieving good results with R&R investments. The working time is set to allow a large portion of the casting industry enough time to prepare investment and fill flasks. However, do make certain you mix the investment with water as long as recommended in the application sheets.
Are there any differences in investment powder preparation or use if I am using plastic, rather than wax, patterns?
How much investment should I have above the wax tree and around the sides of the flask?
Plan to cover the tree with at least an inch of investment and about 1/4” of investment between the wax and the flask walls. This thickness provides good strength for casting.
I do not use investment daily and cannot really justify buying a mixer. Can you suggest any way to mix the material well without having to spend a lot of money?
You can make a fairly good mixer using a portable hand drill, a length of threaded rod, and a rubber disk. Secure the rubber disk to the end of a rod and use the drill to mix the material. If you are mixing a small batch of material, like 2 to 3 pounds, the disk diameter should be about 3”. For a mix of 8-10 pounds, increase the diameter to 6”.
I've noticed that investments seem to heat up a bit while they are mixing. Why?
Gypsum is somewhat exothermic. The more material you mix, the warmer the mix will become. This is not a problem because the vacuum will cool the investment and you may even notice a cooler flask after the second vacuum step.
I have heard people refer to set time, pour time, working time and gloss off time when they speak about investments. Can you provide clear definition of these terms?
Let’s define them from the shortest to the longest time frames. Working time starts when you add the powder to the water and ends when the material starts to thicken. For R&R’s gypsum materials this happens 8-9 minutes after the start of the mix. For our phosphates, this occurs in 4-5 minutes. Pour time starts with the powder to water addition and stops when the material is physically too thick to pour from one vessel to another. Gloss off also starts with the powder to water addition but ends when you can no longer see moisture on the top of the flask. Set time starts at the same point and is timed until a Vicat needle will no longer penetrate the material more than 1 mm deep. Our gypsum products have a set time less than 20 minutes.