But still have to use the silicon ring when casting on top
... which is where I'm having mucho problems with success.
Jim, I may have missed your first thread on this subject. What
type of problems are you having? I cast on top all the time and
rarely have any problems. Are you casting from a tree or directly
from the button? My cast temp is from 900 - 1100 degrees F -
depending on what I am casting. The silicon pad I have is
probably 8 to 10 years old. It has some “battle scars” but still
works fine. I have used the plastic screen to line my flasks
with, but havent noticed any significant differences in my
castings. I usually leave about 1/4 inch air space on the top of
the flask to aid in pulling the vacuum. Maybe if you could
elaborate more on this, we could help more on this subject. Ken
I vacuum 'on top' when I want to do only 1, 2 etc pieces ..
not a whole cylinder .. just don't have any luck on top....
was wondering what sucess others had casting on top of the
unit....
I have to confess, I used uncooked spagetti for vacuum vent
holes. You can leave them in, to bake out. Smells like toast for
a while.
I use common 6 penny nails and hang them around the edge of
the flask by the heads till the investment hardens then pull
them out. Gives nice straight round holes for exhaust. Frank >>
How are you attaching the nails to keep them in place until the
investment hardens? Do you vacuum invest with this method?
How are you attaching the nails to keep them in place until the
investment hardens? Do you vacuum invest with this method?
I vacuum invest then place the nails around the edge of the
flask so that hey hang from the heads on the lip of the flask.
They just hang there with the force of gravity and i let the
investment harden. no trick no wires no secret. May the force be
with you! no pun (at least not a very good one)
Real anxious to try the 1/4 inch vac area at the top… Already
doing hangers… but makes sense… in order to ‘Pull’ the
vacuum on the entire bottom of the flask u need the ‘space’ …
else as I am doing the silicon would ‘suck up’ to the bottom of
the investment and cut off the vacuum…
That’s interesting that u leave a 1/4 inch for the vacuum… I
felt that I shuld leave zero so I screat off the top leaving just
a slight indention … virutually NO air space … I leave about
1/4 inch of investment at the top, cast at 900, using a silicon
pad which has about ‘2’ scourch rings which I try to avoid when I
set the flask.
I use to do trees but due to my poor success, I only pour from
the button now… and still only get 50 percent. I have some
slides that I want to pour but am really afraid too becuse I’ll
lose them!!! or half anyway.
Jim just read your post on 1/4 " at top of flask. From my
experience and what i have read you only want 1/4" to 1/2" of
investment over the top of your highest wax in the flask. also
be sure to scrape the top skin off the investment before burnout
as it tends to form a skin of airtight investment on the top as
the investment sets up. this makes it more difficult to draw
gases through either with vacume or centrifical.
Tried the nails!!! Don’t think so!!! If you don’t get them
just right …WOW, they sink in the investment … Although the
coat hangers are smaller u can bend them over the edge of the
cylinder and … no sinking… so think I’ll stick to the
hangers…
Going to try the ‘straws’ … wonder about the plastic ??
You and Frank were both on track… the 1/4 inch did the trick
…I think… had a small crack in the investment so it wasn’t a
clean pour… But really beleive this will do the job… The 1/4
inch handled the ‘getting the vac up’ problem … like NOW!!! so I
assume the next pour will go fine …
Understand… Just ‘cooked one’ … better results with the
quality… but should have had more investment on top of the
flask as u suggested below… NEXT TIME!!!.. Didn’t know about
the ‘skin’ either so I’ll scrape the cylinder bottom next time to
but all in all, this is the right track…
When using non perf flasks, do you add some sort of aid
spacer to the flask to assist in getting the air out. I use
heated, pinched closed with pliers, plastic straws down the side
of the flask where ever the piece being cast is close. Hold the
straw pieces in place with paper clips for placements and
investing.
John and Cynthia,
I don’t understand the ‘Pinched closed wsith pliers, , plastic
straws down …’
Why pinched and closed and is this done at the vac end of the
cylinder or inserted into the investment???
I don’t understand the ‘Pinched closed wsith pliers, , plastic
straws down …’
Why pinched and closed and is this done at the vac end of the
cylinder or inserted into the investment???
Sorry for the poor info. The straws are heated and pinched
closed so the investment will not fill the straw. The pinched
end goes down into the flask towards the rubber bottom when
pouring the investment, and when casting they will have made
openings towards the vacuum source. One or more of the supplie
houses (Swest, Roi, etc.) carry wax netting that is used to line
the inside of the flask and give the same sort of air/vacuum
lines into the investment.
Sombody questioned the burning of the plastic straws and all I
can say is most wax is patroleum derived, many waxes have plastic
in the mix, so a bit of stray doesn’t bother me too much. If
really a problem, use paper straws (if you can find them!!!).
John
John and Cynthia/MidLife Crisis Enterprises
Maiden Metals/C. T. Designs/ Bloomin’ Wax Works. etc.
PO Bx 44, Philo
CA 95466
Ph 707-895-2635 FAX 707-895-9332
There is no limit to what you can achieve,
if you don’t mind who gets the credit.