Luminar Moldable Sheet (RS-DD) Users Instructions

Users Guide for Luminar Moldable Sheet (RS-DD)

Refractory Sheet Type DD (RS-DD), formerly known as Luminar Moldable Sheet Type LMS, is an advanced material for glass slumping and fusing. No other mold material is as strong, light, versatile, durable, and easy to use. RS-DD has the ability to become pliable while wetted with water and regain its original strength when dried. Thus when it is given a shape when wet; it will retain that form when dry. RS-DD comes as a semi-rigid sheet and is available in four thicknesses: 20, 40, 90 and 120 thousandths of an inch. RS-DD 20 has the least strength and highest moldability. RS-DD 120 has the highest strength and least moldabilty. On firing, a small amount of organic binder burns out and ceramic strength is developed. A fired RS-DD mold will have about 3 times the strength of unfired RS-DD. Once fired RS-DD losses its ability to be molded when wet. RS-DD is immune to thermal shock and, since it is very light, RS-DD has been proven to allow firing rates of 130° F/min in a stationary studio kiln with 1/8″ glass. This manual will describe methods of preparing and using RS-DD molds.


Selection of the best thickness of RS-DD to use is mostly a matter of balancing the strength of a given thickness of RS-DD to the degree of curvature to be developed in the final piece.

When attempting to take a plane surface such as a sheet of RS-DD and form it to a curved surface, such as a deeply bent lamp element, you will observe that a certain amount of “puck- ering” or folding will result. This is because the curved surface has apparently less surface area than the plane surface area started with. This effect is more pronounced when using thicker RS-DD because the difference in the radius between the inner and outer surfaces of the RS-DD is greater. Using the thinnest necessary thickness of RS-DD will minimize any difficulty.

In the event that folds are unavoidable, excess material may be cut away much as a seam- stress would cut a “dart”. Methods of cutting RS-DD are given below. When wetted the RS- DD may be firmly squeezed and held together at the seam to result in a firm bond on drying. The seam can be dressed by burnishing with a damp cellulose sponge. If necessary, irregular- ity may be corrected using ZIRCAR Mold Mix 6 to build up and smooth the seam.


RS-DD may be cut with a utility or exacto knife either wet or dry; although cutting is generally easier when the material is wet.


After the desired shape is cut, the RS-DD is ready to immerse in water. Use a shallow tray and warm water. The piece should be fully submerged. The table below gives soak times for the different thickness of RS-DD.

Sheet Type Soak Time Entire Process Time

RSDD 20 Apply water to one side only

Soak 50 seconds 1 minute

RSDD 40 2 minutes each side 5 – 6 minutes

RSDD 80 4 minutes each side 8 -1 0 minutes

RSDD 120 6 minutes each side 12 -15 minutes

Test for flexibility. The moistened sheet should feel like wet leather. If sheet is not flexible enough, apply more water. If sheet is overly moist, blot up excess water with a paper towel. Any unused wet sheet can be dried and stored flat for re-use.


RS-DD will bond quite firmly to most any surface even glass. To assure easy removal from the pattern, a very thin coat of “Vaseline” should be applied. Once the RS-DD is laid on the pat- tern, it must be held firmly against it in order to accurately replicate its contours. Clothespins around the edges generally work well to hold the RS-DD in place.


RS-DD may be left alone to air dry, although it is often desirable to accelerate drying. This is easily done by warming to 200°F in the kiln. Take care that the pattern you use will able to withstand heating. Once dried, the RS-DD regains its original rigidity.


Prior to firing, it is often desirable to finish the surface of the RS-DD mold. This is easily done using a damp cellulose sponge or finger. The RS-DD surface maybe burnished with either of these until it shines. If the mold is to be used for fusing, give it a coat of ZIRCAR Alumina Rigidizer/Hardener to avoid sticking. This step must be repeated each time the mold is fired for fusing.


No special precautions are necessary to fire an RS-DD mold. As mentioned, the firing can proceed at very rapid rates with no difficulty. However, in the event that the glass is fairly heavy, it will be desirable to pre-fire the mold. This will develop its ceramic strength before it is loaded with glass, thus reducing the possibility of firing some defor- mity as a result of the weight. Once an RS-DD mold is fired, it can be wetted and shaped again.


RS-DD may be used as a fusing, surface for most glass commonly used with the excep- tion of “Wasser Glass” which has a pronounced tendency to adhere to RS-DD. It is critical that the surface of RS-DD be treated with a coat of ZIRCAR Alumina Rigidizer/Hardener each time the RS-DD shelf is fired if adhesion is to be avoided.

Application with a nylon brush is best. Should the surface require dressing after applica- tion of the rigidizer, a damp sponge may be used to gently smooth the surface.

Fire the RS-DD to fusing temperature no faster than 15° F/min. on a flat ceramic kiln shelf prior to use for fusing. The slow firing will avoid warpage and develop the ceramic strength of the RS-DD. It is best to fashion a shelf support of RS-DD for the RS-DD shelf to retain the advantages of RS-DD’s low mass.

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  • ZIRCAR Refractory Composites, Inc.
    P.O. Box 489
    Florida, NY, 10921 USA
    Phone: (845) 651-2200
    Fax: (845) 651-1515