Plaster formula with increased porosity

Patent metadata

Field	Value
Publication number	US-2023382793-A1
Application number	US-202218074664-A
Country	US
Kind code	A1
Filing date	Dec 5, 2022
Priority date	May 27, 2022
Publication date	Nov 30, 2023
Grant date	—

Abstract

In one aspect, a pottery plaster formulation with increased water absorption, comprising alpha stucco, continuously-calcined-in-a-kettle stucco, and a combination of Rochelle salt and one or more of the following: potassium sulfate and/or a phosphate compound. In another aspect, pottery plaster molds with increased water absorption and methods of making and using the pottery plaster molds for slip casting ceramic items.

First claim

We claim:

1 . A pottery plaster composition, wherein the pottery plaster composition is a dry mixture comprising:
alpha-calcined stucco; continuously-calcined-in-a-kettle (CCK) stucco; Rochelle salt; and at least one of the following: potassium sulfate and/or one or more phosphate compounds.

2 . The pottery plaster composition of claim 1 , wherein the pottery plaster composition comprises 5 to 40 wt % of alpha stucco, 60 to 94 wt % of CCK stucco, 0.02 to 0.2 wt % of Rochelle salt and 0.05 to 0.5 wt % of one or more of the following: potassium sulfate and/or one or more phosphate compounds.

3 . The pottery plaster composition of claim 1 , wherein the pottery plaster composition comprises the phosphate compound, and wherein the phosphate compound includes one or more of a trimetaphosphate salt and/or a tetrametaphosphate salt.

4 . The pottery plaster composition of claim 1 , wherein the pottery plaster composition further comprises at least one set-retarding agent.

5 . The pottery plaster composition of claim 1 , wherein the pottery plaster composition consists essentially of:
15-30 wt % alpha-calcined stucco; 70-84 wt % CCK stucco; 0.02-0.1 wt % Rochelle Salt; and 0.05-0.3 wt % potassium sulfate.

6 . The pottery plaster composition of claim 1 having a water absorption capacity of at least 10 wt %, at least 25 wt %, or at least 30 wt %, calculated as an increase in pottery plaster weight measured in the full immersion test at 60 minutes.

7 . The pottery plaster composition of claim 1 , wherein the pottery plaster composition has a shelf-life of at least 6 months.

8 . A pottery plaster slurry comprising the pottery plaster composition of claim 1 and water, wherein the pottery plaster slurry has a water-to-stucco (WSR) ratio by weight in the range from about 0.5 to about 0.9.

9 . The pottery plaster slurry of claim 8 , wherein the pottery plaster slurry further comprises a set-retarding agent.

10 . The pottery plaster slurry of claim 9 , wherein the set retarding agent is used in an amount from about 0.1 wt % to about 5 wt %, based on a weight of the pottery plaster composition.

11 . A method of making a pottery plaster mold, the method comprising:
i) mixing a pottery plaster slurry comprising the pottery plaster composition of claim 1 and water into a mixture; ii) pouring the mixture into a form; and iii) removing the pottery plaster mold from the form after the mixture hardened.

12 . The method of claim 11 , wherein the mixture has a water-to-stucco (WSR) ratio by weight in the range from about 0.5 to about 0.9.

13 . The method of claim 11 , wherein the method further comprises adding to the mixture in step i) one or more set-retarding agents.

14 . A method for slip casting a ceramic article, the method comprising:
i) preparing a clay slip; ii) pouring the clay slip into a pottery plaster mold, wherein the pottery plaster mold contains alpha stucco, CCK stucco, Rochelle salt and one or more of the following: potassium sulfate and/or a phosphate compound; iv) casting a ceramic article in the pottery plaster mold; and v) removing the ceramic article from the pottery plaster mold.

15 . The method of claim 14 , wherein the casting includes removing water from the casting ceramic article under negative pressure applied to the pottery plaster mold.

16 . The method of claim 14 , wherein the method further comprises drying the pottery plaster mold after step v).

17 . The method of claim 16 , wherein the method further comprises repeating steps i) to v) at least once.

Assignees

• United States Gypsum Co

Inventors

• Rosenthal Guy L
• Huch Christian
• Grussing Jeffrey F
• Hargrove Pamela L

Classifications

• C04B28/147 Primary

  beta-hemihydrate · CPC title

• C04B2111/00956

  for making sculptures or artistic casts · CPC title

• C04B11/02 Primary

  Methods and apparatus for} dehydrating gypsum {(for other purposes than cement manufacture C01F11/466) · CPC title

• C04B28/146

  alpha-hemihydrate · CPC title

• C04B24/04

  Carboxylic acids; Salts, anhydrides or esters thereof · CPC title