Document 2RGZNkkQmjdno84gMEogYMbNr
GYPSUM PRODUCTS MANUAL
Chapter V
CERTROCK
Certrock is a specially compounded plaster containing additives which lower the pouring consistency and give it a paint-like flow not found in other plasters, Lecauss of this flow characteristic, Certrock will take the finest detail of a mold and produce casts having extremely smooth surfaces. The low consistency also makes Certrock casts very dense, and high in compressive strength. (About 2-1/2 times stronger than molding plaster.)
There are two grades of Certrock available. Low Consistency and Medium Consistency Low Consistency Certrock is made ov.iy at Blue Rapids and is used mainly for potter/ case molds, Certrock is made at Blue Rapids from white plaster, and at Fort Bodge and Akron from grey plaster. These two products differ from each other in water requirements, Medium Consistency Certrock requiring more water than Low Consistency Certrock to make a pourable slurry. Since Certrock has no period of plasticity, it cannot be build up or screeded into templates.
Lot/ Consistency Ce-rtrock is especially designed for the production of highly detail case molds in potteries and. sanitary ware plants. The high strength and hardness of this material contributes to lower case mold costs through increased wear re sistance and better surface.
PHYSICAL CHARACTERISTICS
Water / Plaster Ratios
Thin Pour
Medium Four
10 parts Low Consistency Certrock
1C paxts Low Consistency Certroc
5 water
lj.-l/2 water
Tensile Strength Tensile Strength
- Wet Average - Dry Average
265 li85
3 GO 580
Compressive Strength - Wet Average Compressive Strength - Dry Average
1700 Ucoo
2CC0 I4I4CO
Setting Time Setting Expansion
- Normal - Normal
15-30 min. 135%
15-30 min. .150%
Low Consistency Certrock is used in making models (poured) fpr' die and mold dupli cating machines, for foundry match plates, for pattern shop"models, statuary, lamp bases, book ends, and for any other purposes where high strength and hardness are desirable in a plaster cast.
The larges volume of sales of Certrock is for the formulation of floor patching and floor underlayment materials. This is generally Medium Consistency material.
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November 1, 1952
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GYPSUil PRODUCTS HAM Util
Chapter V
Thin Poor
li parts water 10 parts plaster
Thick Pour
3-g- parts water 10 parts plaster
Dry Compressive strength Normal Setting Time Setting expansion
5000 - 63CO p.S.'i. 7000 - 7700 p.s.i,
20 - 30 mino
15 - 25 min.
O.llt - 0.16$
0.15 - 0.17$
i'.OTE: Setting time can be adjusted to meet individual requirements.
MIXING DIRECTIONS
Froper mixing of Certrock is important if good results are to be obtained. I material is somewhat confusing "to now users in that it mixes first to a dough which thins out to pouring consistency as mixing is continued. Those unfaniliar with this property tend to assume that more water is needed to thin the mix. Addition of more than the amounts of water shown above will result in failure due to a watery mix. This unusual characteristic of Certrock should be pointed out to new users. Use of a power mixer should always bo re-commended, since hand mixing 0: large batches is rather tiring. Mixing directions should bo followed carefully to obtain best results. For reo.ring consistencies, use 3*5 to ii.O parts of water to 1C parts of Certrock by weight or 3 to 3^ measure s of dry Certrock to 1 measure of water. Stir vigorously for 2 or 3 minutes by hand or preferably by machine mixer, until the initial doughlike consistency has been reduced to a smooth slurry. Pour into mold at once.
The best results are obtained with a prescribed mixture. By using more water, the strength of the cast is reduced and the setting time lengthened. Stronger and harder casts can be made by using less water to form a doughlike consistency, whicl ean be vibrated to fill out details of the mold and remove air bubbles, Certrock should be kept in a dry place before use.
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GYPSUM K.ODUCTS MANUAL
Chapter V
Breakaway Plaster
Eestwall Breakaway Plaster is a special product developed for use in casting expendable mandrels. The aircraft industry uses many hollow shapes of irregular contour such as square ducts, "E" shaped tubes, etc. These are made of Fiberglas cloth which has 'jeon impregnated with a resin and then cured to form a rigid hollow shape. In order to form these hollow shapes, the impregnated glass cloth must be wrapped around a core of mandrel which must be removed after curing the part. Breakaway Plaster is used to cast these mandrels. After the part has been cured on the mandrel, it is immersed in hot water. This causes the special plastei to soften and wash out of the part.
Other industries making irregular shapes of plastic are also prospects for this product which is made at blue Rapids, Kansas. U.S.G. has the only competitive product manufactured at Southard.
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November 1, 1916
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-.FPSUM FIIOOTCTS J'AiflJAL
Chapter V
TUPCAST PIASTER
"Tufcast" is a special plaster product containing an additive which gives the finished cast great resistance to chipping or breaking. This piaster is mixed and cast in the ordinary way. When set, the cast is placed in an atmosphere of steam at atmospheric pressure and "cooked" for a time based on the thickness of the cast, (30 minutes por inch). After processing, the cast is dried in the usual way and devi lops unusual "toughness" in the dry state. This product is excellent for the- production of novelty items such as statues, plaques, etc. since the castings are much more resistant than ordinary plaster casts to damage by shipping and handling.
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GYPSUM PRODUCTS IIANUaL Chapter V
WATER RATIO DATA EQUIVALENTS
WATER Per 100 Plaster
PLASTER
Water Plaster
Per Found Water
= 100
Density
Dry Lbs. Per Cu, Ft.
Percent |
Void i'
Volume j
Total i
Absorption !
Dry Con
pressive Strength Lbs. per Sq. In.
1 1 "` ~ i
/160
i 155
133
123
111;
107
CO uz
100
95K
CO
^
s
s;
89
85
80
76
73
70
67
65
61.5
L 59
? 57
55
53 51.7
5o
f2
Ba
UJ . O^
58.5
57
55.7 52
50UJ
\r-
CO 38
l
UJ Q
35.5
i : 33.3
i 30.0
I 27.0 i 25.0
\ t
\^ 21.0
i
0 lbs.-10 os.
0 lbs,-11 os. 0 lbs.-12 os. 0 lbs.-13 os. 0 lbs<.-l5 os. 0 lbs.-15 oz. 1 lb. - 0 oz. 1 lb. - 1 oz. 1 lb. - 2 oz. 1 lb. - 3 os. 1 lb. - 5 os.
1 lb. - 5 os.
1 lb. - 6 oz.
1 lb. - 7 os. 1 lb. - 8 os. 1 lb. - 9 oz. 1 lb. -10 oz. ?. lb. -11 oz.
1 lb. -12 oz. 1 lb, -13 oz. 1 lb. -15 oz. 1 lb. -15 oz.
2 lbs.- 0 oz. 2 lbs.- 1 oz. 2 lbs.- 2 oz. 2 lbs.- 3 oz. 2 lbs.- 6 os.
2 lbs.- 8 os. 2 lbs.-10 oz. 2 lbs.-13 oz. 3 lbs.- 0 oz.
3 lbs.- 3 oz. 3 lbs.-11 oz. 5 lbs.- 2 oz. 5 lbs.-12 oz.
61 - 39
59 - 51 57 - 53 55 - 55
5T- IS 7
51 - 59
5o - 50 58|-5li
17 - 53 ,46 - 55
15 - 56 53 - 57
52 - 58
51 - 59 50 - 60
39 - 61 38 - 62
37 - 63
36 - 65 35i-65|
35 - 65 35 - 66
33 - 67
321-67-! 32 - 68 31,5-68.6
29 - 71
28jU7ll
27|-72|
26 - 75
25 - 75
25 - 76 21.3-73.7 19.3-30.7 17.5-82.6
(Aoprcccimatc Data)
37.3
50.5
53.2 56.0
TSSTS
51
55.5
56.2
58.5 ""31.0
63 65.3 67
69 71 73.0
75 77
78.5 80.5 82 83,5
85.0
36.5 33.2
89.5 93,8
96,0 99.0 102.0
105.5 110.8 116. 122. 128.
75.3% 72.1 70.2 68.3 66.3 65.8
62.5 61.2
59.6
fStcT
56.5 55.0 53.8
52.5 51.0 55.7 58.5 57.
56.
55.5 53.5 52.5
51.5 50.5 39.2
38.3 35.5
35.0 31.6
29.5 27.0
23.5 , 2'G. ' 16.
11.5
50 p,s,i. 100
2C0 3C0
400
500 650
350
1000
1200 1500
1600
1750
2000 2 ICO
2275 2500
2750
3000 3250 35CO 3650 3750
1
5000
5500
5oco
5500
60C0 7C00 8250 9750
11000 13000 15000 15000
GEi'jITlAL TABLE
shewing effect of quantity of mixing water on Density - Voids - Strength.
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GYPSU31 PRODUCTS HkNUAl
Chapter V
SUPER STRENGTH GYPSUM PRODUCTS
DENSITE
Densite (registered Bestwall Trademark) ir; a relatively new gypsum plaster pro duced at the Bestwall Cyosum Company plant at Blue Rapids for the first time in 19)49, This product is produced by an exclusive patented process involving a unique method of calcination. This process yields a plaster differing markedly from ordinary kettle stucco in physical properties. Crushed rock graded is cooked in a kettle covered with a water solution of . Incidentally, the basic competitive product. United States Gypsum's "Hydrocal" is produced by calcining crushed gypsum under steam pressure.
Densito has the appearance of ordinary white molding plaster. Although it is chemically the same as molding plaster, a given volume of the dry powder weighs about twice as much as an equal volume of molding plaster. It is somewhat similar to U.S.C-. s Hydrocal (registered U.S.G. trademark) but requires considerably less mixing water to obtain a given consistency3 therefore, Densitc1 casts are f-,r harder and stronger than Hydrocal casts. More- recently, U.S.G. has produced a so-called Low Consistency ffrdrocal which, whilo made under a different process, has very similar properties to Densitc.
To obtain plastering consistency only 22 parts of water to 100 parts of Densitc by weight arc required. Casts made at this water/plastcr ratio develop a compressive strength in excess of 13,000 pounds per square inch when dry.
To obtain pouring consistency, only 33 to 3? parts of water are required with base Densite, as compared to 70 parts for Sunflower Holding Plaster and U5 for Hydrocal. Casts made at this pouring consistency (33 water/plaster ratio) de velop a compressive strength of approximately 9,000 pounds per square inch when dry. This is over four times the strength of casts made from molding plaster at the same pouring consistency* i.e., 70 water/plaster ratio.
Densite mixes with viater like ordinary molding or casting plaster and the setting action is also similar to that of molding plaster. Ordinarily, it sets a little faster than molding plaster, but the setting time can be regulated as required to suit a particular use.
Setting expansion at pouring consistency is approximately 0.32% but this can be reduced to as little as .OLt# or increased to as much as l.$% by the addition of certain ingredients.
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GYPSUM FkODUGTS likiRJAl
Chapter V
Base Densite (K-5) is Densite taken directly from the- storage bin and contains no accelerator, retarder, or ether additives.-:, The setting time of base Densite varies slightly from batch to batch, final Gilmore set running on the average about 20 minutes.
Industrially, base Densite is used by dental stone manufacturers, some invest ment casting plants and some gypsum flooring firms. In each case the Densite is used a-s a basic ingredient of a special compound manufactured by our customer. That is, the people who buy base Densite do not use it as such, but add various modifiers to produce finished dental stones, floor patching compounds, invest ment easting compounds, etc.
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I'jovcmbtr 1, 1958
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GIPS DM PRODUCTS MANUAL Chapter V
BESTROCK
Fouring ConsistencySetting time normal job
conditions Setting expansion Dry compressive strength Color
- 35 to 37 lbs. water per 100 lbs. plaster
- 30 to U5 minutes 9-12 to 0.11$
- 6,500 to 7^500 p.s.i, - Dark grey
NOTE: Pours with a viscous flow and is self-leveling.
Uses: (1) Forjinchoring Bolts, Rods, etc., in Conerete
Drill hole large enough to allow at least one-half inch thickness of Bestrode around piece to be anchored, fill hole with water, remove excess water with rag; then put bolt or rod in hole and pour Bestrock around it. As soon as set, while still wet, Bestrock has a compressive strength of over 3,000 p,si.
(2) As a Grout for Levelling Machinery
Fills space compieueiy, due to visccus flow and self-levelling characteristics. Does not shrink as do some grouting materials. Equipment can often be used same day, due to high wet strength.
(3) As^a Floor Patch__or Concrete Floors
Clean the areas to be patched, roughen surface if necessary, dampen and then pour Bestrock. Due to self-levelling proparty, little - if any troweling is necessary. Patch is ready for traffic soon as set, usually in less than one hour.
Bestrock is easy to use. Add required water only, mix and pour. Saves time because it sets hard in one hour or less. (Faster or slower setting time can be furnished if desired.)
Precautions: Bestrock is not recommended for driveways and sidewalks. If used for exterior anchoring, paint with a water resistive coating.
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June 1, 195?
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!. GYPSUM ASSOCIATION
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