Subject : Breather mesh instead of a top platten? Posted : 2021-11-19 12:55 PM Post #38003
Hi, new to the world of veneering, just ordered a pump and bag from Vacupress, can't wait to try it out. I've read on some other sites that using breather mesh provides more clamping power and doesn't require a top platten and also eliminates the need to cut grooves in the bottom platten.
Has anyone tried this method and if so what kind of results did you get?
Subject : RE: Breather mesh instead of a top platten? Posted : 2021-11-22 4:37 PM Post #38004 - In reply to #38003
Your questions gives me an opportunity to speak about this topic of the bleeder mesh, (we call it EvacuNet) and hopefully clear up certain misconceptions. Let me start here, the purpose of any mesh, grooved platen board, stick and even a piece of string, is to provide a pathway for the air to get down to the exit port and out of the bag, thats it. As long as the air get out of the bag, which method gets used doesnt matter, one is not better than another. The secondary issue is only which method gets the air out as fast as the pump wants to evacuate it. As single piece string over your panel to the exit nipple is going to take the pump longer to draw the air out than a grooved platen or bleeder mesh. But….this really only matters with a auto self cycling pump.
A grooved platen board is by far the most efficient air evacuation method as the grooves provide “little rivers” so to speak, that all converge at the exit hole. Where as bleeder mesh allows the air to “trickle” through it, which is fine, but for auto self cycling pumps the platen board is a better bet. Not to mention the platen board is better for sliding your panels in and out on top of, less wear and tear on the bag. If you just dont want to take the time to make a platen, bleeder mesh is surely easier and quicker to set up.
As far as a bleeder mesh type product providing more clamping power, that is simply nonsense. Once the air is fully out of the bag the pressure you get is simply whatever the pump is pulling. Also, having a caul between the bag and veneer is always a good idea. A rigid caul such as a piece of MDF, particle board, or plywood provide a hard leveling surface that prevents veneer from possibly wrinkling. The soft flexible nature of a bleeder mesh can allow veneer to be slightly wavy or wrinkle, and can also leave marks in the veneer. Also, for clarification, I call a platen board what goes under your panel that has grooves in it. What goes on top and provides this leveling pressure on the veneer I call a caul.
One more thing, if you use a grooved platen board the addition of a bleeder mesh is unnecessary. The platen board does the job just fine. No need to have both.
Subject : RE: Breather mesh instead of a top platten? Posted : 2022-01-07 8:58 PM Post #38005 - In reply to #38003
I always use a breather mesh with no top platen. I simply use heavy duty fiberglass window screen (pet resistant variety, which is ~ 3 x thicker than typical screen). One advantage is that if the item you are veneering is not perfectly flat, the breather mesh will completely comform to the surface, and give much more even pressure than a perfectly flat top platen would. Sometimes I veneer surfaces that are intentionally curved, in which case the use of breather mesh without top platen is essential. So both approaches can work, but I recommend the breather mesh only approach as being simpler and more versatile.
Subject : RE: Breather mesh instead of a top platten? Posted : 2022-01-09 6:41 PM Post #38006 - In reply to #38003
For spreading adhesive on the core, I use a foam paint roller. An attempt is made to leave a consistent thickness of adhesive across the entire surface, but cannot be guaranteed with a paint roller. Typical veneer is very flexible, and will conform to the glue surface below it. And the veneer itself seldom is perfectly flat. A flexible breather nesh like Evacunet can initially conform to an uneven glue layer to which the veneer has conformed, or even to mild wrinkles and other unevenness in the veneer itself. Under vacuum, it seems to me the also flexible bag will conform to the surface below it and then apply uniform pressure on that surface without necessarily making the underlying surface flat. So there would seem to be a possibility that simply placing a breathable mesh between the veneer and bag may leave the eventual veneer surface less than perfectly flat, creating a situation where one might sand through the veneer at high spots. Even a 1/4" thick top caul would seem inflexible enough to force flat the veneer surface below it, in the process forcing the underlying glue layer to a more even thickness.
Preparing and using a 1/4" top caul adds little time and cost to the project and for me is a very worthwhile undertaking.