Document rxxZxO1gabkLG93RZ2OX25eZE

&E5TWAIL GYPSUM COMPANY INDUSTRIAL GYPSUM DIVISION BULLETIN NO. 164 March I, 1962 \ BESTWALL POTTERY PLASTER Bestwall Pottery Plaster is a new pottery plaster from our new gypsum plants located at Brunswick, Ga., New Orleans, La., and Wilmington, Del. It was developed by the Bestwall research laboratories to satisfy the known needs of the Pottery Industry for a pottery plaster with uniform absorption, uniform grind, uniform consistency and uniform setting time. Bestwall Pottery Plaster is light green in color insuring easier mold inspection and less eye strain. INSURE HIGH QUALITY WARE WITH HIGH QUALITY MOLDS OF BESTWALL POTTERY PLASTER. Other literature available from Bestwall for the Ceramic Industry. #3 #5 #205 #206 Field Test Procedure - Pottery Plaster Mechanical Mixing of Plaster Bestwall Pottery Plasters for the Ceramic Industry Check List - Common Troubles - Pottery Mold Shops SGP 0026139 DENSITE GYPSUM CEMENTS MOULDING PLASTERS STATUARY PLASTERS DENSFLOR CERTROCK ORTHOPEDIC PLASTERS POTTERY PLASTERS PLATE GLASS PLASTERS SPECIAL INDUSTRIAL PLASTERS BESTWALL GYPSUM COMPANY . 120 EAST LANCASTER AVENUE ARDMORE, PENNSYLVANIA GEORGIA- RAC IFIC GYPSUM division INDUSTRIAL PLASTER CHECK LIST - COMMON TROUBLES - POTTERY MOLD SHOPS BULLETIN NO. 206 The best insurance against trouble is using sound practices at all levels of production. Good mold shop practices can be summarized as follows: 1. Plaster stock is rotated. The oldest is used first. 2. Plaster is' stored in a dry and warm area. 3. Uniform mold density is assured by maintaining careful control of consistency used by the shop. Plaster and water are both weighed. 4- The soaking and mixing times are carefully controlled by time switches on the mixer. 5. Only water fit to drink is used and it is always used at the same temperature. 6. Molds ore carefully dried at 125 F. with forced air before they are put into use. 7. Mechanical mixers with properly designed buckets and propellers are used or a continuous mixer of proper size and design is used. 8. Molds are treated as precision tools. They are handled with care and stored carefully. 9. The casting shops keep close checks on each mold's performance. When trouble is experienced, the mold shop foreman should examine the problem to see which of the above conditions are being ignored. The best procedure is, of course, to see that the rules are not violated in the first place. In the table that follows there is a list of the more common troubles encountered in pottery mold shops. Probable causes and suggested cures are shown for each trouble. SGP 0026135 DENSITE AND DENSCAL GYPSUM CEMENT MOLDING PLASTERS STATUARY PLASTERS DENSFLOR CERTROCK ORTHOPEDIC PLASTERS POTTERY PLASTERS PLATE GLASS PLASTERS SPECIAL INDUSTRIAL PLASTERS GEORGIA-PACIFIC / GYPSUM GIViS ON C a M M Q U A fc- jU i'-QRTl AND (IRECinN IF THE TROUBLE IS: 1. Slow set 2. Snap set 3. Lumpy plaster INVESTIGATE: Mixing speed Mixing time Water temperature Age of plaster Contamination in bag Contamination in bin Contamination in mixing Exposure to water 4. Soft molds before use 5. Hard molds before use 6. Excessive expansion 7. Soft molds after use 8. Chalky molds after use 9. Efflorescence 10. Pinholes Mix consistency Burning in drying Mix consistency Mix consistency Water temperature Mixing time Sweating-out Drying Burning in drying Contamination Poor drying Soaking Mixing 11. Hard spots 12. Rough surface Mixing Drying Soaping Not creamed in Mix coarse plaster CORRECT BY: Mix faster Mix longer Use warm water (Add accelerator) Use fresh plaster Open fresh bag -- Check storage Clean bin - Screen plaster Clean mixer -- Clean bucket Determine where wetting occurs In bag -- In bin - While in storage - While in transit? Take appropriate action. Decrease water Lower oven temperature Increase water Increase water Increase temperature Decrease time Dry at 125 F. with forced hot air. Decrease temperature Dry so evaporation takes place from back. Increase soaking time 25 Pitch propeller blades Position propeller shaft 15 from vertical. Use bucket of proper design. Increase soaking time -- sift plaster into water. Dry so evaporation takes place from back of mold. Use less soap Increase mixing time Use only high quality pottery plaster. SGP 0026136 IF THE TROUBLE IS: 13. Cracked molds INVESTIGATE: Handling Thermal shock Burning 14- Warped molds (Uneven drying) Parting compound Plaster quality 15- Short life Wrong type plaster Excessive soap Hard spots Efflorescence Pinholes Mixing 16. Low Absorption 17. Mildew 18- Voids on surface Used while green Handling Consistency Soft molds Dirty mold Wrong consistency Wrong plaster Not dry Trapped air in mixing Trapped air in pouring 19. Poor fit Worn-out Poor design CORRECT BY: Handle molds with care Protect hot molds from drafts Use special thermal shock plaster Decrease temperature in drying Decrease drying time Wash mold to remove parting compound Use only high quality pottery plaster Use only high quality pottery plaster Clean molds - use less soap See *11 on preceding page See * 9 on preceding page See *10 on preceding page Use clear water Weigh water and plaster Sift plaster into water Soak until all plaster is wet Time soaking period Use mechanical mixer Use clean equipment Mix until creamed Control mixing time Dry molds before using Draw to attention of Supervisory Personnel Adjust consistency See *1 on preceding page Keeps molds clean Mix at higher consistency Use only high quality pottery plaster Wash molds Dry molds thoroughly See #10 on preceding page Pour plaster while still fluid Pour deepest part of cavity first Pour plaster so it flows over surface Make new case molds Redesign SGP 0026137 The following graph illustrates the importance of controlling use consistency (consistency is the parts water per hundred parts plaster by weight.) *K-59 Pottery Plaster is one of several superior plasters for the ceramic industry produced by Georgia-Pacific. Write us direct or ask our technical salesman for our Bulletin No. 205, "Industrial Plasters for Ceramic Industry" and Bulletin No. 5, 'Mechanical Mixing of Plaster. SGP 0026138