CERAMICS TECH

GLAZE RECIPES





Plaster Calculator  excel file



NOTES ON ACHIEVING COLOR IN GLAZES:

ADDING VEE GUM AND CMC TO A GLAZE

 

UMF CALCULATOR 

           Glaze Calculator:  Batch to UMF and UMF to Batch by Matt Katz from Matt and Dave's Clays
           requires Excel or Download OpenOffice for Free

UMF CALCULATOR VERSION 2 (try this if the other version didn't work with PC)

 

Glaze Test Variation Sheets: Blank





    Plaster Calculator Download

     

    NOTES ON WORKING WITH PLASTER:

    Pottery Plaster Mix For Wedging Tables:
    For wedging boards or tables mix 70 parts of water to 100 parts plaster. This equals 4.17 gallons water per 50 pounds dry pottery plaster.
    Product Data
    – The best material available for sanitaryware and dinnerware casting.
    – Formulated for long life and reduced breakage (stronger molds).
    – Available with or without thermal shock additive.
    #1 POTTERY PLASTER is highly uniform, noted for outstanding performance and long life. The standard of the industry - this is the best material available for sanitaryware and dinnerware casting. Used for making plaster bats, wedging boards, and working molds. This is a relatively soft plaster which may be used for carving.
    Technical Properties                                                               English     Metric  
    Use Consistency (parts of water by weight per 100 parts plaster )          70     70      
    1 Hr. Compressive Strength                                                      1,000 psi     6.8 MN/m2      
    Dry Compressive Strength                                                        2,400 psi     16.3 MN/m2      
    Total Absorption Capacity                                                                 36%     36%      
    Maximum Setting Expansion                                                         0.210%     0.210%      
    Density Wet                                                                            99.0 lb/ft3     1.58 g/cm3      
    Dry                                                                                        69.0 lb/ft3     1.10 g/cm3      
    Set Time (Machine Mix)*                                                          14-24 min.     14-24 min.      
    General Directions and Guidelines 
    Preparing the Mix Use potable water at temperatures between 70° and 100° F (21° and 38° C). Since variations in slurry (the plaster and water mixture) temperature produce variations in setting time, it is important to keep both the plaster and water in a stable temperature environment prior to use. The higher the temperature of the water, the shorter the set time. Weigh both the plaster and water for each mix. The water-to-plaster ratio is critical because it governs both the strength and the absorptive capacity of the mold.
    Soaking Sift or strew the plaster into water slowly and evenly. Do not drop handfuls of plaster directly into the water. Allow soaking for 1-2 minutes. The plaster should be fully dispersed in the water prior to mixing. Small batches require less soaking than large batches. See bulletin IG503 for specific soaking instructions.
    Mixing Mixing the plaster slurry is one of the most important steps in producing plaster molds with maximum strength, absorption, hardness, and other important properties.
    Mechanically mixed plasters develop uniform molds with optimal strengths. Plasters can be mechanically mixed through
    both batch and continuous processes. Proper blade and bucket dimensions are important for obtaining the best batch mix
    (see IG503 for details). Longer mixing times result in higher mold strength and shorter setting times.
    Pouring To prevent air entrainment and provide a uniform, smooth surface, careful pouring of the plaster slurry is necessary. Agitation of the filled case mold is a further step used to prevent air at or near the mold surface. Whenever possible, the plaster slurry should be poured carefully in the deepest area so the slurry flows evenly across the surface of the case mold.
    Pouring a large amount of slurry directly on the face of the case mold may result in slight densification of the plaster mold
    at the point where it strikes the surface of the case. This produces a hard spot, giving uneven absorption.
    Drying All pottery molds should be dried as quickly as is safely possible after manufacture so that maximum physical properties can develop. Dry to a constant weight.
    The best drying rooms or ovens provide (1) uniform and rapid circulation (minimum of 15-30 fps) of air with no “dead spots” having little or no air movement, (2) equal temperatures throughout the entire area, and (3) provisions for exhausting a portion of the air while replacing it with fresh air. High humidity surrounding the drying room or oven inhibits the efficiency of the drying because the air pulled into the room is incapable of picking up much moisture from the molds. The maximum temperature at which plaster molds are safe from calcination is 120° F (49° C). With substantial free water in
    the mold, higher drying temperatures can be used without difficulty. As drying progresses, the temperature must be reduced to prevent calcination. The safe drying zone is in the shaded area of graph (below, right). Before removing molds from the dryer, the temperature should approach that of the area around the dryer to prevent thermal shock.
    Mixing Ratios for slipcasting molds. No. 1 Pottery Plaster
    Water
    Plaster
    1/2 Pint
    11oz
    1 Pint
    1 lb 6 oz
    1 Quart
    2 lb 12 oz
    1.5 Quarts
    4 lb 2 oz
    2 Quarts
    5 lb 8 oz
    2.5 Quarts
    6 lb 14 oz
    3 Quarts
    8 lb 4 oz
    3.5 Quarts
    9 lb 10 oz
    1 Gallon
    11 lb
    1.5 Gallons
    16 lb 8 oz
    2 Gallons
    22 lb
    2.5 Gallons
    27 lb 8 oz
    3 Gallons
    33 lbs




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