vacuum degassing silicone query
- Thread starter zorg
- Start date
Rebelscum
Sr Member
No chance I'm afraid.
IEDBOUNTYHUNTER
Sr Member
You need 28" Hg to degass RTV. No shop vac will even come close.
I use a Robinair 2-stage vaccum pumpthat I paicked up on ebay for about $150
I was looking at these, so they work ok? Do you think its strong enough for vac forming.
Al
There was a good post on the 405th about making your own degassing chamber with a cheaper harbor freight pump. Rube, the member who came up with this, was able to pull 27"hg with this set-up.
I believe the pump at harbor freight is around $16
thanks for the info guys, i didnt realise it expanded that much, good tip.
are those white pipes drainage types?
thanks for your response chaps
-z
Rebelscum
Sr Member
This is my vacuum rig cart. It has the small vacuum chamber I got from my local smooth-on dealer, but it only does about 16oz at a time due to the massive expansion when degassing. The large one is a thick cooking stock pot with a thick piece of acrylic on it that I cut a groove in and filled with mold rubber. Then I just drilled and tapped a hole for a brass fitting to hook stick the vacuum hose on. The pot is sized to comfortably hold a 5 gallon plastic paint bucket.
Last edited:
Robinair one works GREAT ! Bought mine two years ago
on EVILBAY and runs like a CHAMP !
:thumbsup
Small bit o' trivia if your needing a wee-bit more rubber
de-gassed then you feel " safe " about because of expansion !
Pour your rubber into you pail DAYS before you
de-gas ! Naturally, over time, many of the air bubbles will
work thier out and the volume of expansion can be minimized !
Mind you, NOT ELIMINATED ! :lol
That sucker WILL still expand, but not nearly as bad
as if you JUST pour rubber into you pail 5 minutes ago !
:cool
Yodajammies
Sr Member
How does silicone cure rubber react to being in an open container for several days?
Won't hurt it at all.... I've worked in a shop where
we had poured rubber into pails and left it sit for
WEEKS at a time.. Nothin' happened... :cool
Rubber won't last " forever ", but it's NOT like Resin
where if you keep RESIN in open containers moisture will
destroy it !!!!! :confused
we had poured rubber into pails and left it sit for
WEEKS at a time.. Nothin' happened... :cool
Rubber won't last " forever ", but it's NOT like Resin
where if you keep RESIN in open containers moisture will
destroy it !!!!! :confused
clonesix
Master Member
I am confused as to the value of letting RTV resin sit out in the open for days? The air that you are trying to degass from the silicone was mixed in when the catalyst was blended into the rubber.
I use a mixer and a drill motor to mix the RTV, because my arms would break trying to mix it by hand. It mixes in a lot of air. This is why I built the vacuum chamber.
I use a 65 qt. Heavy Duty aluminum stock pot from ebay, and 1" thick plexiglass for the lid. There is a 1/4" rubber gasket between two.
Yes, the RTV expands like a balloon when degassing, so you need to be able to place a lage enough container into the chamber. Mine will hole a 5-gallon bucket.
I use a mixer and a drill motor to mix the RTV, because my arms would break trying to mix it by hand. It mixes in a lot of air. This is why I built the vacuum chamber.
I use a 65 qt. Heavy Duty aluminum stock pot from ebay, and 1" thick plexiglass for the lid. There is a 1/4" rubber gasket between two.
Yes, the RTV expands like a balloon when degassing, so you need to be able to place a lage enough container into the chamber. Mine will hole a 5-gallon bucket.
Last edited:
When I say " leave it sit out " I do NOT mean a gallon
at a time or anything !!!! :lol
I'm talking about small amounts since most people
DON'T have big 5 gallon pots to put the pails INTO
for degassing!
When I say leave it sit out, I am talking only something like
5 - 10 oz's or so ? That small amount won't matter if left sitting
for a few days..
NO, I wouldn't recommend pouring out a gallon from a bucket
into a pail and leaving it sit as that sucker WON'T have too
many bubbles rise out on it's own !
:cool
at a time or anything !!!! :lol
I'm talking about small amounts since most people
DON'T have big 5 gallon pots to put the pails INTO
for degassing!
When I say leave it sit out, I am talking only something like
5 - 10 oz's or so ? That small amount won't matter if left sitting
for a few days..
NO, I wouldn't recommend pouring out a gallon from a bucket
into a pail and leaving it sit as that sucker WON'T have too
many bubbles rise out on it's own !
:cool
But whayt is being said is if you leave it out you are doing nothing because then when you mix in the catalyst you will then create the air bubbles, it can not sit out at this point as it will cure...........what I do as I can not afford a vac chamber right now is brush a very thin coat onto the master first, this allowes the air to excape then pour the rest of the rtv into the mold...........there are many air bubbles but not on the surface of the mold!!:love
exoray
Master Member
That pump setup makes little sense... The HF venturi pump runs off an air compressor it will pull the ~27" just fine on it's own, why the brake bleeder hand pump?
I used the guts from one of those HF venturi pumps in my old setup before I picked up a $20 electric pump at a garage sale... They work great for what they are...
robn1
Master Member
I looked at the original thread, he said he just used the bleeder pump for the vacuum gage, I guess it's what he had on hand. 405th.com/forums/index.php?showtopic=15685&st=320&p=271894&hl=degas&fromsearch=1&#entry271894
This is my vacuum rig cart. It has the small vacuum chamber I got from my local smooth-on dealer, but it only does about 16oz at a time due to the massive expansion when degassing. The large one is a thick cooking stock pot with a thick piece of acrylic on it that I cut a groove in and filled with mold rubber. Then I just drilled and tapped a hole for a brass fitting to hook stick the vacuum hose on. The pot is sized to comfortably hold a 5 gallon plastic paint bucket.
thats sucks!
boom boom
you have all the toys philip, nice set up.:thumbsup
i wonder if someone could send me over one of those harbour freight pumps to the u.k.?
-z
Last edited:
Rebelscum
Sr Member
I'll be happy to send you one.
Similar threads
