Cool Tools Ring Pellet Mold - Half Sizes

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Sku : RMK-103

4" x 4"

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Cool Tools Ring Pellet Mold - Half Sizes

Ring Pellet Mold in half sizes, 4.5 through 12.5. Can be used with Ultra-Smooth Investment for years of service.

Download our complete instructions for casting your own ring sizers here.
Click here for our Ring Sizer Instructions, which include our exclusive ring forming chart for rings that won't tear during firing. Ring sizers are single use and dissolve in water after firing. 

Cavities are filled with a batter-like casting powder which dries to a hard pellet that does not shrink in the kiln. The pellets are used to assure accurate metal clay ring sizes during firing. Pellets dissolve in water after use.

Made in the USA


Making Metal Clay Rings

Making a ring from metal clay may seem a little intimidating at first, but it's actually very easy. We have listed the essential tools you'll need and give you ring building fundamentals to get you started.

Basic Ring Forming Tools

Finger gauge - to measure a finger for ring size

Ring Mandrel - to form a ring

Ring Sizer Pellets - to control the size of a ring

Waterproof Mandrel Paper - to keep a formed ring from shrink-locking to the mandrel during drying

Invisible Tape - to make a tube from mandrel paper

Finger Gauges

A finger gauge is used to determine ring size. There are several different types: ring-style finger gauges, paper gauges and strip gauges.

Ring-style gauge - a set of plastic or metal rings. There is one ring in each size that can be tried on until the proper size is found. Ring-style gauges are available in plastic and metal. The plastic gauges tend to have sizes on only whole and half sizes but are most economical. Metal gauges often have quarter and three-quarter sizes. The most expensive metal ring gauges come in wide and thin bands.Strip gauge - works like a cable tie. A plastic strip is cinched onto the finger and reveals the size at a plastic stop. The plastic strip will measure in whole, half, quarter and three-quarter sizes.

Ring Mandrels

A ring mandrel is used to form a ring on. Mandrels may be individual rods or a single mandrel that is either stepped or tapered. A ring can be formed to the most common sizes with any of the mandrel types. Here is a detailed description of the main types of mandrels that can be used for ring making:

Silicone Ring Mandrels

Our non-stick silicone ring mandrels are the perfect tool for making rings or cylinders in metal clay. When mounted on our mandrel stand, these silicone ring mandrels are the perfect device for easily forming metal clay into any round object. No longer is wax paper or other non-stick lubricants necessary between the mandrel and your creation. Great for forming wet clay and also for refining or augmenting clay in the greenware state. Removes easily from the non-stick silicone mandrel, when ready to fire. Add 2 sizes for a standard band and 3 sizes for a wide band.


The Multi Mandrel is lightweight and was designed for creating wax ring models, but it's absolutely great for making metal clay rings. The set of 6 ring size mandrels are 5" long. There are two sizes on each mandrel. The smallest mandrel has size 4 on one end and 5 on the other; the largest has sizes 14 and 15. The mandrel is fitted into a stud on the mandrel stand. The stand can be placed so the mandrel is horizontal or vertical. The mandrels can be rotated on the stud, giving you access to every possible angle. The mandrels are available in whole and half sizes, and in aluminum or wood. A wood storage rack to store the mandrels is also available. The double-ended mandrels offer lots of ring-making real estate with no tapers to throw off your sizing. Multiple projects can be created simultaneously. The only drawback to this system is that you cannot use the mandrels to round or size a ring. We recommend the aluminum version over wood because the wood can expand with humidity and can be damaged much more easily than aluminum.

Tapered Ring Mandrel

Tapered ring mandrels are made of steel so the metalworker can form metal with mallets and hammers. There are mandrels with sizes engraved into the steel, and there are mandrels with no markings at all. A finger gauge can be used to mark the right size on an unmarked mandrel. Any tapered mandrel will affect the accuracy of the ring size on wide rings. A wide ring formed on a tapered mandrel will have a difference of 1 to 1-1/2 ring sizes from one side of the band to the other which can result in a ring that is too tight or doesn't fit at all. To overcome this problem, be sure to center the middle of the ring at your desired size on the mandrel for a good fit. We also recommend that you make a wide ring one size larger to account for the width. A wide ring will always feel tighter than one with a narrow band of the same size. Some mandrels have a hole in the end to allow them to bit fitted on a stand, and there are also mandrel rests to hold the stand. This version is not recommended for use with metal clay.

Another type of tapered mandrel is made of wood. A wooden tapered mandrel is made for polishing rings. We do not recommend using this type of mandrel because a ring polishing mandrel is much shorter than a steel mandrel, which means the taper is more extreme. This mandrel is very handy for polishing or stone setting, drying and drilling.

Tapered aluminum mandrels are called ring sticks. A ring stick is a gauge meant for finding the size of a ring. The ring is slipped onto the mandrel and the size is determined by the markings on the ring stick.

A stand is available for aluminum and steel tapered mandrels that raise them off the work surface by about 3", giving you plenty of room to work. If you don't want to invest in a stand, a simple set of feet can be made from polymer clay.

Stepped Ring Mandrel

Stepped ring mandrels have about 1 inch of space for each ring size. Some stepped mandrels come already mounted on a rotating stand, making them very handy for metal clay ring making, but a bit heavier than the Multi-Mandrel system.

Mandrel Sleeve

To make a sleeve, cut a strip of waterproof mandrel paper about 1" wide and 3" long. Wrap the paper, shiny side out, around the mandrel. Trim the strip so one end just overlaps the other end and use a small piece of tape (about 1/4 inch long) to hold it in place. Make sure the tape is on the paper only so the sleeve can be slid off later. Test to be sure you haven't taped the paper to the mandrel.

Ring Sizers

A Ring Sizer is a special pellet or plug that is placed inside the ring shank during firing to control the size. The pellet is made from a special material that does not shrink or burn during firing. As the metal clay sinters, it shrinks tightly around the pellet so the ring is the exact diameter of the pellet after firing. After cooling, the ring is put into water to dissolve the pellet. Rings cannot be formed directly on Ring Sizer Pellets because they would not have any room to shrink and would tear.

Metal Clay Ring Sizers

Cool Tools Ring Sizers are pre-cast pellets available in half and whole US ring sizes from 4 to 12. Match the ring sizer pellet size to the ring size you wear. Our Metal Clay Ring Sizers have the size molded into the end of the pellet so there is never a mix-up in sizes.

Ring Sizer Mold

The Cool Tools Ring Sizer Mold is a cost-effective way for metal clay artists to cast their own Metal Clay Ring Sizer Pellets as needed. The molds are available in whole, half and gang sizes. A half sized mold creates one pellet of each half size from 4 to 12. A whole size mold makes one pellet of each whole size from 4 to 12. A Gang mold make 9 pellets all the same size. You'll need investment or paper clay to cast the Ring Sizer Pellets.


product that is used in casting metals. Investment is mixed and poured into the Ring Sizer Mold to cast ring sizers. Any type of silver, gold or platinum casting investment can be used; however the mold works best with a crystobolite-based product. Crystobolite is a silica-bearing product, so it must be used with a dust mask, or use a silica-free investment.

Our Ultra-Smooth investment makes Ring Sizer Pellets that are very smooth and strong, do not shrink, and can be de-molded in 25 minutes after pouring. They can also be used immediately after de-molding even though they are still slightly damp.

Silica-Free Investment is an alternative that does not contain crystobolite. Ring Sizer Pellets made from Silica-Free Investment are not as dense as traditional investment, and require 2 hours to set up before they can be de-molded, and must be allowed to dry completely before use. When casting with silica-free investment, a soapy-water release must be sprayed into the mold to avoid sticking which is made simply by adding a few drops of soap to plain water in a spray bottle.

What Metal Clay Works Best?

Sterling silver clays, such as EZ960®, should be your first choice in choosing a clay in which to create a ring, as it is much harder and more durable than fine silver clays. Sintered fine silver is soft and brittle, so it dings up pretty quickly and it's fairly easy to break when its thin. Any sterling silver metal clay is our recommendation for rings. Please follow the package instructions.

Recommended Firing Schedule for Silver Clay Rings: EZ960: 1675°F / 912°C for 2 hours in a digitally controlled kiln provides maximum strength. If you are firing flat, and then bending the metal post firing, we recommend 1675°F for a full 4 hours to ensure complete sintering and absolute maximum strength. It is always a good idea to create a test strip before firing your project. We do not recommend torch firing EZ960.

All orders placed before 12:00 (CST) will ship the same day, Monday through Friday. Orders placed after 12:00 (CST) will ship the next day, Monday through Friday. If there is a problem with processing your order, we will contact you.

Free Shipping: US Orders Over $125.00

Paragon & Evenheat Kilns ship separately, and take 2 - 3 weeks to be delivered, direct from the manufacturer.

Same-Day Shipping

Orders before 12:00 pm CST, M-F

Next-Day Shipping

Orders after 12:00 pm CST, M-F

Free Shipping

U.S. Orders Over $125.00

Kiln Shipping

2-3 weeks delivery for Paragon