USG DRYSTONE Casting Media Mixing Procedures - Manual

Successful mixing and use of D RY S TONE ™
Casting Media require the following specific
standards and procedures. To obtain the full
benefit of this product, shop practices and pro-
cedures must follow the following recommenda-
tions.
D RY S TONE Casting Media-To-Water Ratio
The recommended ratio is 100 lb. of D RY S TONE
Casting Media to 18-20 lb. of water. It is vitally
important to always weigh the water and
D
RY S TONE Casting Media powder. Variations in
the D RY S TONE Casting Media-to-water ratio will
affect performance characteristics and physical
properties.
Water Purity
Water used in mixing D
RY S TONE Casting
Media should be as pure as possible. If water is
drinkable, it probably is suitable for the mixing
of D
RY S TONE Casting Media. In many cases,
water for industrial use is taken from contami-
nated sources and is high in organic impurities
that will lengthen the setting time of
D
RY S TONE Casting Media. These and other
contaminates could negatively affect the prod-
uct and ultimately the finished cast.
Water Temperature
Variations in water temperature will significant-
ly affect setting time and workability, and can
cause difficulty controlling mixing times. The
rule of thumb is that cold water retards set and
warmer water accelerates set. (Both temperature
extremes thicken the mix.) It is highly recom-
mended that the temperature of both the water
and the D
RY S TONE Casting Media be between
70 and 80 °F.
Mixing
The uniform mixing of D
RY S TONE Casting
Media is very important in producing casts with
maximum strength and hardness since there is
a direct relationship between energy input dur-
ing mixing and strength development of the
cast. Changes in mixing procedures will have a
great effect on the finished product.
An ideal mix is one in which the powder
particles are completely dispersed in the water
to produce a uniform, homogeneous slurry.
To mix D RY S TONE Casting Media properly
for uniform casts, follow these easy steps:
1. Weigh the D
RY S TONE Casting Media and
water accurately for each mix, preferably
with a digital scale.
2. Sift or strew 1 ⁄
2
to 2 ⁄
3
of the D RY S TONE
Casting Media into the water slowly and
evenly. Use the proper mechanical mixer
and mixing bucket (see Fig. 1).
3. Start mixing to incorporate this material into
the water immediately.
4. Once incorporated, continue to add the
remaining D RY S TONE Casting Media to the
mix.
5. Continue mixing until all the powder is
incorporated.
6. Mix for a total of 2-4 minutes until the prop-
er fluidity is achieved.
Depending on actual batch size, adjust-
ments can be made to the mixing cycles.
Typically, larger batches may require slightly
longer mixing cycles.
For best results use the recommended
mixer/mixer motor combination as indicated in
Figure 1. The mixing shaft should be main-
tained at an angle 15° from vertical. The shaft
should be about half-way between the center
and the side of the container. The propeller or
J
IFFY ® mixer should clear the bottom of the
container by 1 to 2 inches, forcing the mix
downward.
Generally only one propeller is necessary,
but where this does not provide enough turbu-
lence, use two per shaft or use a larger diame-
ter propeller.
Keep all equipment clean to avoid accelera-
tion of the reaction between the water and the
D
RY S TONE Casting Media.
Pouring D RY S TONE Casting Media
D RY S TONE Casting Media can be used with
most mold materials such as silicone, latex, or
urethane-type molds.
To prepare the mold, make sure it is clean,
then dip the mold or spray it with a suitable
mold rinse. Using a steady rate, pour the
D
RY S TONE Casting Media slurry into one cor-
ner of the mold or on the highest point and
allow the slurry to rise and seek its own level.
To minimize air entrainment, mechanically
vibrate or shake the mold or the surface onto
which the mold is placed.
Pour the mold slightly less than full.
Continue to vibrate the molds until no new air
bubbles are seen rising. Help draw out trapped
air by inserting and withdrawing a spatula, stir-
ring stick, or brush into the D
RY S TONE Casting
Media slurry.
Top off the mold, slightly overfilling. Vibrate
once more, then screed the surface smooth.
Demold the D
RY S TONE Casting Media cast
material when it reaches peak heat.
To aid in the drying and cooling down
process, remove the hardened D RY S TONE
Casting Media cast from the mold, or loosen the
mold walls and allow air to circulate the cast.
D
RY S TONE Casting Media products can be dec-
orated approximately 2-4 hours after set time.
United States Gypsum Company
D
RY
S
TONE
™ Casting Media
Mixing Procedures
Figure 1. Mixer and mixing bucket recommendations
Batch Size Bucket Dimensions Mixing Blade-Size/Type Mixing Motor
Pounds D RY S TONE Total Mix Volume h=height
d=diameter
Volume
<20 lb. <1.8 gal. h=10 Љ d=8.5Љ 2.5 gal. 2-3 Љ prop/J
IFFY 3 ⁄
8
Љ, 2500 rpm drill
20-50 lb. 1.8 to h=13
Љ d=11Љ
5.4 gal. 4
Љ prop/3.75Љ J
IFFY 3 ⁄
8
Љ, 2500 rpm drill
4.5 gal. h=17
Љ d=12Љ
11.8 gal. 4
Љ prop/3.75Љ J
IFFY 1 ⁄
2
Љ, 1200 rpm drill
50-100 lb. 4.5-9 gal. h=22 Љ d=14Љ 14.7 gal. 4 Љ prop/5Љ J
IFFY 1 ⁄
2
Љ, 1200 rpm drill
1. Mixing vessel should be appropriately sized to contain D RY S TONE Casting Media slurry volume, assuming that density of slurry is approximately 130 lb./ft. 3 at a water to D RY S TONE Casting Media ratio of 0.19 to 1.
2. Mixing vessel dimensions should maximize height and minimize diameter such that the height:diameter ratio is 1.2:1.6.
3. Either a J
IFFY mixer or prop blade should be used for agitation. The blade diameter should be approximately 1 ⁄ 3 the diameter of the mixing vessel.
4. Mixing motor should provide 1000-2000 RPM under load.
5. Prop Mixer should be a three blade, 25°-pitch propeller of appropriate diameter.