Measuring and Mixing Design-Cast 66

Before you start, make sure that the mixer and container are clean and free from residue from a previous batch.

Mixing ratio for DESIGN-CAST 66

100 parts by weight of DRY MIX (part A)
10 parts by weight of POLYMER (part B)
16 to 23 parts by weight of WATER

YIELD (without added aggregate): about 18 cubic inches per pound of DRY MIX or one-third (1/3) square foot per pound of DRY MIX at a typical thickness of three-eighths (3/8) inch.

CONSISTENCY of the mix ranges from a stiff putty, to a soft clay, to a paste, depending on how much water you use.

Use a scale (preferably a beam scale for accuracy) to measure each of the ingredients: dry mix, polymer, water, and pigment if used. AVOID EXCEEDING THE MAXIMUM RATIO AMOUNT OF WATER—too much water tends to weaken the piece.

In order to achieve maximum strength, freedom from cracks, and consistent setting times, mix DESIGN-CAST with a mechanical mixer—not by hand. You can mix batches up to about 20 lbs. using a Jiffy^® mixer, or a propeller-type mixer chucked into an electric drill or air-operated power tool. The recommended mixing speed for DC-66 is typically about 1,000 RPM. Heavy or clay-like consistencies should be mixed more slowly (i.e. about 300 to 600 RPM.) A rule of thumb to assure proper mixing is that the propeller diameter should be about a third (1/3) to a half (1/2) of the diameter of the mixing container, and that the mixing part should be completely submerged in to mix to avoid sucking air into the mix.

A suitable mixing container is a plastic bucket, a plastic salad or Ice-cream container, or a stainless steel pail

For best results, mix materials at 75°F (23°C) or cooler. A lower temperature will give you a longer working time; however, do not expose the polymer to freezing temperatures.

Recommended mixing procedure

1. Place the measured amount of polymer in the mixing container.
2. Add the measured amount of water in the mixing container.
3. Add all of the dry mix (and pigment, if used) for the batch.
4. Mix about 30 seconds.
5. Let the mix rest 3 minutes.
6. Re-mix for another 30 seconds.

Longer mixing times will reduce the working time, but will otherwise not harm the material. In any case, mix long enough to give a uniform, lump-free mixture. For addition of fiberglass or aggregates, see the section on Reinforcing Design-Cast 66.