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PRIMCOTE binder provides foundries with shell coats that dry quickly while reducing, or eliminating, common metal defects caused by buckling, lifting and cracking. PRIMCOTE binder contains a wetting agent, an antifoam and a color indicator to monitor shell dryness. This binder is premixed and ready to use.
1. Remix the PRIMCOTE binder prior to use to ensure a homogeneous blend of material.
2. For best results, weigh all ingredients when making up a new slurry or making additions to an existing slurry.
3. When building the slurry, add the refractory last. If more than one refractory is used, add the lowest density refractory first: fused silicas (2.2 g/cc), alumino silicates (2.7 g/cc), zircon (4.5 g/ cc). Add refractory slowly for best results.
4. New and makeup slurries must be prepared with a propeller mixer, not in a rotating tank. This ensures proper dispersion of the refractory particles. The propeller mixer must be of adequate HP and RPM. Excessive mixing action can introduce air into the slurry and cause erratic viscosity and/or bubbles in the slurry coat.
5. As with any slurry, the viscosity of the slurry must be stable before use. A stable viscosity is one that does not change by more than 1 second when checked at 1 hour intervals. Viscosity can be increased by adding more refractory and decreased by adding more binder.
6. It is required to replace water lost to evaporation. When water is needed (based on test results for viscosity and/or binder solids), use distilled or deionized water as opposed to tap water, which can contain contaminants that can negatively affect slurry life.
7. Antifoam, wetting and bactericide agents are already formulated into PRIMCOTE binder and other additions may not be compatible. Contact R&R’s technical team before making these additions to the slurry.
8. Patterns must be clean and free from silicones or other contaminants before dipping.
9. It is not usually necessary to use a prewet before applying the first primary coat to the wax pattern. If a prewet is needed, use PRIMCOTE binder only.
10. If a prewet is needed between coats, the PRIMCOTE binder should be diluted to 26% binder solids (binder to water ratio of 5.8:1 by volume, 6.9:1 by weight). Drain the prewet well so that no pockets of liquid are left on the pattern.