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Investment - how to mix?


How much do you use for 1/2 lb mix with water ?.


Hi Brian

I’m assuming your question is how much water should be mixed with 1/2
lb of investment. The normal proportions is to add investment to 40%
of its weight in water. This makes the water content of the mixture a
little under 30%. I weigh out both my investment and mixing water
because it is more accurate than using volumetric measure. I also
work in metric measures with digital scales accurate to 1 gram. 1/2
lb of investment is roughly 225 grams and this would need to be added
to 90 grams (90ml) of water and mixed. For this sort of work it is
much easier to work in metric measures.

All the best
Jenifer Gow


I use Kerr Satin Cast 20 and they recommend for my tall flask (5" x
3.5") 2lb of investment and 344ml of distilled water., for my short
flask (3" x 3.5") 1.5lb of investment and 274ml of water, and for my
small flask (3" x 2.5") 12oz of investment, 136ml of water.

The Kerr company has a detailed chart on their website (in a. pdf)
but I suck so bad in math, I just called them and told them I was
too stupid to read their charts and had the tech guys there walk me
through the numbers for my individual needs.

The ratios of investment to water makes the difference between a
good casting with no porosity and no flashing, and a bad casting.
There’s no wiggle room.

I use a Pyrex graduated measuring cylinder and am cognizant of the
concave meniscus created by water in glass.

The meniscus is the curve seen at the top of a liquid in response to
its container. One must measure so that the line you are reading is
even with the center of the meniscus. For water and most liquids,
this is the bottom of the meniscus.


I have a mixing casting chart. I would share if anyone is

Andy “The Tool Guy” Kroungold


I wonder how long investment lasts. I have some that has not been
used for several years… is there a way to test is w/out wasting
wax…thanks in advance…


To have the best results when figuring out ratios of water and
investment isto use a chart that tells how much water in cc’s for
the size flask you areusing, multiply that measurement by 2.5, that
is the grams of investment. Cubic centimeters (cc) and milliliters
are equal. I totally suck at math, this system works! Measuring
water in those plastic containers with milliliterand cc marking is
VERY inaccurate. I used to do 9 3" x 7" flasks with 50-75 pieces in
each flask three times a week, for about 12 years, over a million
pieces cast. Weigh water, weigh investment, accurate method. I mix
water and investment for 1 1/2 minutes, vacuum mixed investment for
1 1/2 minutes, pour into flask, vacuum for 1 1/2 minutes.


Folks here are going to be horrified, but Tim and I don’t measure
and we use tap water.

We mix with our fingers. Yup. Our formula is to mix investment and
cold tap water the thickness of Belgian waffle batter. Not waffle
batter, but Belgian waffle batter. Just a tiny hair thinner than
waffle batter.

We vacuum twice. Once in the bowl and once in the flask.

We buy big barrels of investment. It takes us a while to go through

I like to roll a closed barrel periodically to keep the different
particles well mixed.

We always get great results.

The last time we lost a casting was years ago when our kiln went
crazy and melted the flasks.

I know. So low tech. But it has worked for us for decades.

Have fun and make lots of jewelry.
Jo Haemer

Folks here are going to be horrified, but Tim and I don't measure
and we use tap water.
We vacuum twice. Once in the bowl and once in the flask. 

I vacuum twice too, just like you. Speaking of being horrified. My
thermocouple went south many years ago and I just stopped worrying
about temperature.

I turn my oven on high, and when the flask is just under glowing I
turn it off. Then when it’s looking right, I cast.

I’ve recently got a hold of a temperature thingy and discovered I was
casting at around 900-1000 F. by eye.

Paf Dvorak

How much do you use for 1/2 lb mix with water? 

I recommend contacting the manufacturer of the investment and asking
them to teach you how to correctly mix their product.

Ratios are critical.

Paf Dvorak