Vacuum veneering with a shop vac?

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Forum topic by bbasiaga posted 03-27-2015 10:40 PM 1079 views 0 times favorited 6 replies Add to Favorites Watch
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1234 posts in 2023 days

03-27-2015 10:40 PM

Not sure I’ve got this in the right forum, but here goes:

Anyone vacuum veneer with a shop vac as the vacuum source? I have done vaccum forming of plastics and this technique uses a vacuum box powered by a shop vac. The plastic (heated) itself acts like the vacucm bag and gets sucked down over a mold.

Wondering if that technique could be adapted to veenering? Would the shop vac provide enough force?


-- Part of engineering is to know when to put your calculator down and pick up your tools.

6 replies so far

View Steve Peterson's profile

Steve Peterson

377 posts in 3110 days

#1 posted 03-27-2015 11:22 PM

Never tried it, but it seems risky. A shop vac may only produce a small fraction of the vacuum that a real vacuum pump can produce. The noise is going to be really high. And the shop vac might overheat if it depends on air flow for cooling.

The difference between vacuum forming and vacuum veneering is the length of time required. Vacuum forming may only need to run for a few minutes. Vacuum veneering may need an hour or more for the glue to set.

If you have a large air compressor, you might look into a venturi vacuum generator. They are significantly cheaper than true vacuum pumps.

-- Steve

View CaptainSkully's profile


1601 posts in 3587 days

#2 posted 03-27-2015 11:29 PM

West Systems makes a venturi nozzle for vacuum bagging that works with the air compressor you probably already have. It’s over $200, but comes as a kit that includes the plastic and a bunch of other stuff. I’ve used it to make longboards. Full disclosure, this website is part of my parent company, however, the testimonial is 100% accurate and I have no vested interest in West Systems as a company.

-- You can't control the wind, but you can trim your sails

View macatlin1's profile


78 posts in 2971 days

#3 posted 03-28-2015 12:15 PM

I agree with Steve that a shop vacuum might not have enough suction and you will run the risk of burning out the motor if it uses the vacuum air to cool the motor. That said, I have used both the venturi and the vacuum together. The venturi will pull a strong vacuum but not deliver a high flow rate so if the bag contains a large amount of air to start it will take a long time to exhaust it. While the shop vacuum will exhaust a large volume of air but will not pull a large vacuum.

Set up the bag with the venturi attached and running. Make a patch from some bagging material and sealant. Cut a small “x” cut in the bag no larger than the shop vacuum nozzle and apply the shop vac nozzle over the “x” to exhaust the majority of the air. No need to use any sealant on the nozzle and you can remove the nozzle and cover the “x” hole with your hand to let the vacuum breathe if needed. When the shop vacuum becomes ineffective slap on the patch and let the venturi take over.

I worked at a company that made large composite items and this was standard practice to get the laminate under vacuum as quickly as possible.

View Don Butler's profile

Don Butler

1092 posts in 3423 days

#4 posted 03-28-2015 12:41 PM

I’m just wondering – -—?

Has anyone tried to use Space Bags for veneering?

I’m just sayin’ – – – – – -


-- No trees were damaged in posting this message, but thousands of electrons were seriously inconvenienced.

View Fred Hargis's profile

Fred Hargis

5002 posts in 2521 days

#5 posted 03-28-2015 12:48 PM

I remember Wood magazine tested the Space Bag idea, and it didn’t work. I’d have to look it up, I can’t remember why it didn’t work but I think it may have been they couldn’t get enough vacuum on the bag. I dod remember this wasn’t an articel, but rather an answer to someone asking about it in the “ask Wood” section.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Ripthorn's profile


1458 posts in 3013 days

#6 posted 03-28-2015 12:50 PM

I have vacuum veneered a couple of guitars using HF space bags and my shop vac. I had pretty good success, but it did take a couple of tries. The things I found most useful are:

- Use a rubber brayer or hard roller to get as much air out as possible (I was using highly figured veneer on a contoured surface)
- Make sure the veneer is good an soft. I bought some veneer softener at Woodcraft that turned out to just be a glycerin/water mix, so you can totally make your own
- If you are going to be doing bookmatching, glue the leafs together and smooth the seams prior to putting on the substrate
- Put the veneer face on the opposite side of the space bag as the valve (meaning the valve is on the back side of your work piece
- Use window screen as bleeder mesh
- Don’t let the veneer overhang the workpiece much at all
- Especially with space bags, I would draw the vacuum and wait to see if it lost it (best done dry at least once), if it holds, then I check back every 10 minutes or so for the first hour. Try to feel for any air pockets through the bag.
- Don’t run the shop vac continuously, you’ll burn out the motor. Just draw down the vacuum and let the bag hold it, occasionally touching it up as necessary.

On the whole it worked pretty well, I am pleased with the result, but I would only do it for the occasional piece here and there.

-- Brian T. - Exact science is not an exact science

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