We need a solution to our investing problems.
We use flasks that are 3 by 3 inches, we’re at an elevation of
7,000ft above sea level.
And we use Satin Cast.
The question is what do you do differently in a much higher
elevation?
Where I work we invest and cast at sea level, and use a
de-bubblizer. My boss is setting up another studio at 7,000 feet
above sea level.
The investment is setting up too fast and is full of bubbles and the
castings are coming out terribly.
We use flasks that are 3 by 3 inches, we’re at an elevation of
7,000ft above sea level. And we use Satin Cast.
The question is what do you do differently in a much higher
elevation?
Thank you for your help!
Valerie
Water behaves very differently at the higher altitude. It has a much
lower boiling point.
There are a limited number of jewelers casting at such high
altitudes.
You could write the manufacturer and ask them what they suggest.
Here’s an out-of-the-box idea if you don’t get a helpful response.
This may sound strange, but ask people who cook at high altitudes to
see what changes they make to account for how the water acts
differently. I can’t promise it will be helpful advice when you
translate the ideas they give you to casting investment, but there
are a lot more people cooking than casting at that altitude. You
might get lucky. Betty Crocker or other cooking sites might have
info on how to handle it also.
Hi Valerie,
I like you am fortunate to have a studio at sea level allowing the
full weight of atmospheric pressure to utilized during vacuum
investing for lost wax casting. High altitude studios apparently have
problems with bubbles on cast surfaces,while I’ve not had this
problem others have and I can refer you to an article on the Hoover
and Strong website with a possible solution. Read it heRe:
While I’m not affiliated with Hoover and Strong I am a pretty
satisfied customer. Be sure to let us know how it works out.
Mike Edwards
Hi Valerie,
I am at 5000 ft. and I use the directions as they are on the Satin
Cast instructions and have no problems. One thing I have found the
instructions say to use water that is between 70 deg F and 90 deg F
and when I use the lower temperature water it sets up a little
slower. You might want to try even colder water.
I have a paper I have put together for a beginner casting class that
has the process that I use and it is step by step. Since I have
started using this procedure I have not had a bad investment. I have
attached a copy of it.
I hope this might help.
Ken Moore
[Edit]
Attachment removed:
How can I share files and pictures with the list?
http://www.ganoksin.com/gnkurl/ftp
Or… send the files to the attention of service@ganoksin.com and
we will upload them for you…
[/Edit]
I have heard but not tried that using hot water (110F) will
improve high altitude investing. That it will make the investment
less viscous so less problems with bubbles but it will set up much
faster. It would be worth an experiment.
James Binnion
James Binnion Metal Arts
Hi guys,
David W.raises an interesting thought with the idea of checking
cooking sites-like Betty Crocker etc. My in-laws lived in
Albuquerque NM and when visiting I would always make allowances in
temperature & timing when baking…John & I live here at sea
level,also. As a native Calif/Bay Area person, I found this to be a
bit of a challenge but certainly doable… I would think that you
could also check with the investment manufacturer because they have
created a product that can be used at various locations. As Ken
Moore pointed out, he is at 5000’ level and using Satin Cast 20–it
works fine…
Remember, when one bakes at higher altitude, there are adjustments
that must be done and it would seem logical that this happens here.
Cheers from foggy SF,
Jo-Ann Maggiora Donivan
http://www.donivanandmaggiora.com
Ken,
I’d like to have a copy of your paper as I’m about to start my first
casting and need all the help I can get!
Thanks,
John in Indiana
I have heard but not tried that using hot water (110F) will improve high altitude investing. That it will make the investment less viscous so less problems with bubbles but it will set up much faster. It would be worth an experiment.
You compensate for the faster set up time when using hot or warmer
water, by using a bit more water, which then delays thickening and
setup.
My employers casting setup has a single high speed vac pump for both
investing and casting. As I said, high speed, since it can pull a
good vacuum on a fairly large bell jar reasonably quickly. But it’s
not all that HIGH vacuum. It may be simply too much plumbing in
valves, hoses, etc, between driving both a casting well and an
investing table, leading to air leaks, but getting a really decent
vacuum to get investment to decently boil (a good thing, as the
agitation helps loosen and remove any stubborn tiny bubbles, and it
also continues mixing the investment, giving an even more uniform
water/powder emulsion than you get just from mechanical mixing). So I
help it. Slightly warmer water means the mix will boil at a slightly
lesser vacuum, so doing this (easy simply because our casting room
tends to be hot anyway, so the water for investing is what’s been
sitting in it’s jar at room temp, perhaps high 70s temp range). The
powder too has been in that room, so both are slightly warmer than
“standard” room temperatures. That means the investment will boil
better than if I mixed it with 70 degree water. But then it sets too
fast at a 40:100 ratio, so I use about 42:100. The result is a
thinner mix, it boils better, and sets in the right predictable
amount of time. Works well. Haven’t had an investment failure in
years.
Peter
At altitude you have a problem with vapour pressure-basically water
boils at a lower temperature. What I would do is degas the water
BEFORE mixing it with your investment plaster. Once done you can
store the water in a sealed container for a day before using. You can
also use more water than the recommended amount but leave the
investment for a longer time to set as the setting is a chemical as
well as physical reaction.
Nick Royall
What I would do is degas the water BEFORE mixing it with your investment plaster.
Mold makers in the ceramics industry do this when mixing plaster in
a very low-tech way. Apparently tap water contains more dissolved gas
than water that has just sat out for a while. So the plan is to draw
the water the day before you need it. This is also a way to let the
H2O stabilize to ambient room temperature. I keep several open gallon
jugs of water in the investment area and refill for the next time
while I am waiting for the flasks to set. Honestly, I cannot say that
this makes too much difference from when I just use water straight
from the tap, as long as I get it to room temperature. The ceramic
mold guys don’t generally vacuum their material, so I think it makes
a bigger difference for them.
Steve Walker
Ceramic plaster moulds are made from a plaster which has a retardant
added to it that slows the setting rate. They also use a much
greater water to plaster ratio so unfortunately it is not really
possible to compare the two as like for like.
At altitude the triple point for water is not 0 deg C so there will
always be a problem with vapour pressure (steam). removing the air
from water will prevent its liberation as the plaster reacts and
warms up so minimising the amount of gas liberated by this heating.
You could use cooled boiled water but as a vacuum pump is available
it takes no real effort to remove the air from the water beforehand
and this allows you to mix the plaster/water and pour without further
vacuuming if you are careful, which then lessens the amount of gas
liberated when the investment is setting. Give it a try, I’m sure
you will see an improvement.
The same applies in areas of the world which are below sea level,
the vacuuming of the water changes its viscosity and removes the
elasticity that dissolved air gives water- a standard for hydraulic
systems.
Nick Royall