Safe vacuum levels for mason jars & likes

R

rashid11

Joined
Dec 8, 2005
Messages
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Folx,

I will be stabilizing some burl soon, via vacuum method . Was wondering what are safe levels that typical mason jars (say 4" x ~8" tall) can handle before they implode ?

I can pump down to some serious vacuum. Clearly, after certain levels one reaches point of diminishing results. I will place the jars inside of a larger plastic container to contain the mess should things go awry.

I will be judging the thing visually, looking for intense bubbling action to begin and will stop pumping shortly thereafter.

To answer the likely questions - I am one of those weird types that like to do everything by themselves :) .
 
The problem with mayonnaise jars ,and similar mason jars, is that they are not all equal. One may implode at 20" vac, and another will take 24". I would not approach any more than 24" and would be leery above 20". Getting or making a proper tank with a view window or bell dome is a better choice.
Stacy
 
I'm not going to comment on jars, as I am with Stacy on this. After observing the effects of labware implosion a number of times over the years, I can't overemphasize the need for good scatter shielding with questionable containers. I had a lab accident when I was a newbie that scattered glass dust 20 feet away from a 1L container implosion.

One effect you need to watch for as you experiment, Rashid, is to notice that there will probably be two phases of bubbles. When you first apply vacuum, you will be boiling any solvent in the substrate, the effect of something called latent heat. That will slow down as the mixture cools from the effects of evaporation. You will then probably observe a slower, finer bubbling which is the actual evacuation of the interstitial air in the wood. You want to wait until that segment is completed.

When I experimented with home stabilizing, I ended up buying a HF pressure can for spray painting, so I could pressurize to try and force stabilant across the fiber membrane.
 
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I don't know your setup, but I'd place each jar in a 5 gallon bucket of water while you're pumping them down. Weights may be necessary to hold them underwater.
 
Don't risk your eyes and skin, jar implosions are little glass grenades. Get a proper chamber or bell jar

-Page
 
I have had people tell me there is no risk from an implosion, since the glass moves inward. This is bunk. The resulting implosion can rebound and throw the glass like a hand grenade. I avoided sounding like my usual self, but I will say it now. "Only a fool would use a mason jar as a vacuum chamber." I am sure there are hundreds of those who have, and they didn't get hurt....but that did not make it any safer. Get or maker a proper chamber.
Stacy
 
What is a safe and in-expensive window material to use when making one of these?
 
Safety first is my approach here. In my signature fashion :) I shall report on me findings with a video which will hopefully help the collective with the process.

Again, not aimed @ pros - these either buy pre-stabilized or send theirs out for stabilization, but rather @ DYI types.

The goal is to have ez to reproduce, dirt-cheap and uber safe setup for stabilizing smaller size scales @ one's shop, using stuff from a nearby HD or Lowe's .

I suspect that pre-cut to 3/8 (and dry) pieces of typical burl will barely require any vacuum at all for the wood hardener (common item) to penetrate across.
 
To address this correctly, I'm sure all of our individual shops have stuff and contraptions
OSHA would not approve of, and don't recommend doing it the way I do it.
I use a two jar system the outer jar being a 2 quart olive jar with a roll roofing gasket
in the lid. The other jar (with the liquid) goes inside. I draw 28 to 28.5 inches of vaccum
using minwax wood hardner, watco polyurethane mix, lemon oil, oil dye,--you get the idea. Usually 1.5 square block of wood will sink in an hour in wood hardener. HF sells a device for emptying auto air conditioners for about $10, hook it to shop air and draw the vac. I haven't used any special jars and no problems but again this works for me in my
shop and I'm not reccomending it for any one else.
 
It's not the vacuum as much as the pressure. As I understand the process you draw a vacuum and then apply pressure. That's where you would get into trouble with the jar.
Just what I think,
Lynn
 
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