Why are some vacuum chambers marked "no wood"

Signed-In Members Don't See This Ad

Valin6210

Member
Joined
Jul 31, 2021
Messages
18
Location
Webster, NY
I was looking into vacuum and pressure chambers to get into stabilization, casting and blank making. On Amazon I noticed a lot of vacuum tank systems say "not for wood" or "no wood" in their description. I don't understand why this would be the case or are they just doing CYA for liability?

I already have a vacuum pump setup for veneering so was able to throw together an easy mason jar setup for my initial experiments but someday would like to get a larger pot and want to understand why some put the "no wood" wording in there.

Cheers,
-Rich
 
Signed-In Members Don't See This Ad

Dehn0045

Member
Joined
Mar 19, 2017
Messages
1,530
Location
Houston, Texas
My understanding is the lids are made of Plexiglas (pmma) and most wood stabilizers use acrylate resin, which does not play nice with Plexiglas. Although they will work fine for a while (especially if you don't spill liquid on them), eventually the lids crack and then fail completely. I believe that the ones designed for wood use glass lids.
 
Last edited:

egnald

Member
Joined
Jun 9, 2017
Messages
928
Location
Columbus, Nebraska, USA
Greetings from Nebraska.

I am pretty sure Dehn0045 is correct. Before wood stabilization became widespread there were a lot of folks out there putting together chambers for de-gassing paints and such, and most of them used 1/2-inch thick Plexiglas(R) acrylic lids which are only marginally thick enough. Combined with the practice of causing stress points by drilling holes in them for gauges and such, and as Dehn0045 stated, the stabilizing chemistry would start to react with them resulting in a catastrophic failure. (I personally experienced such a failure even with a 3/4-inch thick plexiglass lid - it was an impressive implosion and scared the living crap out of me)!

So, when wood stabilization took off the blame for catastrophic failures was widely put on the chemical interaction between stabilizing chemicals and plexiglass and rather than substantially increasing the thickness of the lid or changing the material to Lexan(R) polycarbonate (better) or glass (best) and substantially increasing the cost, many simply added the "Not for Wood Stabilizing" warning. Over time it may have simply become a boilerplate disclaimer for anything that comes with an acrylic lid.

After my implosion, I used a step drill and mounted the inlet/outlet and gauge through the stainless steel rather than going through the lid and switched to 3/4-inch Lexan(R) polycarbonate for the lid, but after several uses it looked like there might be some crazing on the surface. Having a strong motivation to never, never ever, experience an implosion in my shop again, I finally replaced the lid with one made of glass and have been stabilizing relatively anxiety free ever since.

Although many have had success with less than optimal configurations, my recommendation is to 1) Avoid plexiglass and opt for polycarbonate or glass if possible; 2) Opt for the thickest lid material you can find within reason; and 3) Avoid lids that have holes drilled through them if possible.

Dave

PS Plexiglass has become the genericized trademark for acrylic products such as Plexiglas(R), Lucite(R), Acrylite(R), and Perspex(R). Polycarbonate brands include Lexan(R), Hyzod(R), Markrolon(R), Susta(R), Tuffak(R), and Tecanat(TM).
 
Last edited:

RobS

Member
Joined
Jun 20, 2016
Messages
895
Location
Carlsbad, CA
These are the 2 chambers I own, stabilizing is not cheap. You tend to get what you pay for. Lots of people have had a lot of issues with instruments in the lid. So I have gone with the following:

I love my turntex chamber and have had it for 5 years.

I use the slick vac for degassing silicone molds but it can also be used for stabilizing,
 

Bats

Member
Joined
Oct 12, 2020
Messages
355
Location
W. Nowhere, CT
I have yet to suffer an implosion, but after ruining the transparency of my original (acrylic) lid trying to use Minwax Wood Hardener (yeah, smart move - lucky it didn't trash the pump and/or ignite. I was young(er) and stupid(er)) I've gone through two (also acrylic - one 1/2", one 3/4") replacements - both of which spiderwebbed during the course of the first 24hr run with Cactus Juice.

I've since picked up a Turntex chamber, but the layout, while great for pen blanks, just isn't very good for things like degassing (and I have yet to find a container that works in the Turntex chamber for smaller quantities of blanks/resin when dying), where a wider flat surface is helpful. I've thought about punching a hole in the side and going for a glass lid like Dave, but it's only a 1.5gal and that would put the pump inlet worryingly close to the bottom. So for the moment it collects dust.
 

Jans husband

Member
Joined
May 4, 2020
Messages
185
Location
Doncaster England
These are the 2 chambers I own, stabilizing is not cheap. You tend to get what you pay for. Lots of people have had a lot of issues with instruments in the lid. So I have gone with the following:

I love my turntex chamber and have had it for 5 years.

I use the slick vac for degassing silicone molds but it can also be used for stabilizing,
Sorry all, but I want to understand the processes of stabilising and casting.
I see references to Pressure Pots and Vacuum Chambers, but can you explain which pot is used for what in the pen turning world.
Can you use either for both processes?
I have done resin casting of blanks without a pot, but you will all know that bubbles tend to be a problem, which I have dealt with by vibration of the mould following casting, but no stabilising so far.
Please treat me as an uninformed Newbie, that way I may get answers I understand!!
Mike
 

Dehn0045

Member
Joined
Mar 19, 2017
Messages
1,530
Location
Houston, Texas
@Jans husband you use a pressure pot for casting (to collapse small air bubbles while the resin is curing) and a vacuum chamber for stabilizing. In general you cant use a vacuum chamber for pressure - they are typically not rated for pressures needed for casting, and even if they were the lids are typically designed to use the vacuum to hold and seal. You can use a pressure pot for vacuum, but I don't think they are typically designed to seal as well (a small leak on a vacuum system can cause problems whereas a small leak on a pressure system might not be an issue). Also, vacuum pots are usually designed such that you can see inside with the system closed, this helps you to see what is going on and prevent messes and other issues. If you use a pressure pot for vacuum then you're going to be running blind. With the cost of resin being what it is, you're probably better to purchase or build a proper pot for the job versus trying to get by using one pot for both jobs. Just my 2 cents.
 

RobS

Member
Joined
Jun 20, 2016
Messages
895
Location
Carlsbad, CA
Sorry all, but I want to understand the processes of stabilising and casting.
I see references to Pressure Pots and Vacuum Chambers, but can you explain which pot is used for what in the pen turning world.
Can you use either for both processes?
I have done resin casting of blanks without a pot, but you will all know that bubbles tend to be a problem, which I have dealt with by vibration of the mould following casting, but no stabilising so far.
Please treat me as an uninformed Newbie, that way I may get answers I understand!!
Mike
The 2 vacuum chambers i listed are full pulling vacuum only. They are made for that and only that. You can use them to degas silicone, or to stabilize. Pulling vacuum on dry wood soaking in stabilizer pulls out all the air, and when you release the vacuum the wood soaks up stabilizer.

Pressure pots are designed to hold pressure not vacuum. Casting blanks under pressure, helps make bubbles collapse and appear no existent.
 

magpens

Member
Joined
Feb 2, 2011
Messages
15,281
Location
Coquitlam, BC, Canada

Jans husband

Member
Joined
May 4, 2020
Messages
185
Location
Doncaster England
Many thanks to you all for those posts.
Sorry, I should have started a new thread rather than hijack someone else. Sorry!!
All a lot clearer now!
A pressure pot seems to be the way forward for me to cast blanks successfully, but I was interested in the tutorial list which Mal suggested which gave the method for casting bubble free without a pot-with a bit of extra faffing!
Mike
 
Top Bottom