JoeWoodworker
JoeWoodworker Veneer
The Official Website of this Non-Professional Woodworker ™

Part 1
Introduction

Welcome
Veneering Basics

14 Good Reasons
Vacuum Press Uses
Vacuum Press Options
Overview

Questions & Answers
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Part 2a (Option 1 of 2)
Project: V2 Venturi Press

About Project: V2
Parts List
Build the Manifold
Build the Reservoirs
Assemble the Venturi
Make the Carrier
Wire the Press
Testing and Adjusting
Mods and Options
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Part 2b (Option 2 of 2)
Project: EVS Pump Press

About Project: EVS
Parts List
Pump Selection
Build the Manifold
Build the Sub-Manifold
Build the Reservoirs
Make the Carrier
Final Assembly
Wire the Press
Testing and Adjusting
Mods and Options
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Part 3
Vacuum Bagging

Vacuum Bag Basics
Polyurethane vs. Vinyl
DIY Vacuum Bags (A)
DIY Vacuum Bags (B)
Connect the Bag
Bag Closures
Bag Platens
Breather Mesh
Maintenance
DIY Frame Press

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Part 4
Veneer Information

About Veneer
Veneering Glossary
Veneering Myths
Backer Veneer

Veneer Glues
Veneering Tips
Substrate Materials
Flattening Veneers
A Sharp Veneer Saw
Jointing Veneers
Taping Veneers
Dealing with Defects
Curing Glued Panels
Veneering w/o Vacuum
Hammer Veneering
Iron-On Veneering
Veneer Storage
Amazing Bookmatches
Copper Veneer Guide
Paperbacked Veneer

Edgebanding Guide
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Part 5
Miscellaneous Info

Vacuum Forming
Vacuum Chucking
Vacuum Clamping
Vacuum Clamp Matrix
Vacuum Infusing
DIY Vacuum Manifold
Vacuum Press Gallery 1
Vacuum Press Gallery 2
Veneering FAQ
Veneer Glue FAQ
The Vac FAQ
Copper Veneer FAQ
Downloads (PDF's)

VeneerSupplies.com

Vacuum Veneering - Tips, Tricks, and More

Breather Mesh in Action!Breather mesh is a plastic fabric used in a vacuum bag to allow air to flow away from the project being pressed and towards the vacuum port or valve stem. It is used in place of a top platen/caul. Without it, the vacuum bag material will seal against itself or the veneer causing pockets of reduced pressure.

Thse pockets of insufficient vacuum inside the bag, greatly reduce the clamping strength needed to press the veneer down onto the substrate. By using breather mesh, you allow the vacuum to evenly distribute throughout the bag and this is the key to successful vacuum pressing.

A bottom platen board (typically 3/4" melamine) is still required when breather mesh is used but with this method, there is no need to cut grooves in it. For flat veneer panels, the bottom platen is only used to provide a reference surface which keeps the panel flat while the veneer adhesive is setting up. For curved projects, the mesh acts as a flexible top platen that comforms to the shape of the project.

Breather Mesh Advantages

  • Light weight
  • Inexpensive
  • Re-usable
  • Allows you to see the veneer as it is being pressed
  • Does not fatigue the bag material
  • Reduces bleed-through artifacts
  • Easy to use, cut, and store
  • Will not stick to most veneer adhesives

It was once thought that breather mesh was only suitable for curved projects in which a standard caul would not be usable. However, you’ll find this material excellent for use with flat panel veneering as well. Here are some tips for using breather mesh on your next vacuum press project.

Dont Forget!

Breather mesh can have sharp edges. Some readers have suggested covering the edges of the breather mesh with duct tape.



The Ideal Set-Up for Most Flat Panels
If you have a small project to veneer, you may not be using the full width or length of the vacuum bag. In this case, insert a platen and place your veneer and glued-up substrate on top. Then place the breather mesh over the entire veneer surface leaving a few inches of over-hang at the edge closest to the valve stem. Position the entire assembly so that the valve stem on the bag is above the overhanging breather mesh. This will allow you to evenly distribute vacuum over the veneered panel.


Note that the breather mesh and bottom platen
are larger than the project panel.
 

Vacuum Mesh Bridging
If your breather mesh is just barely large enough to cover the project or if you want to keep the valve stem off the veneered panel, you can cut a small strip of breather mesh from any over-hanging side and place it between the main part of the mesh and the valve stem. The "bridge" piece should lay on top of the mesh that covers the project. I've done this with a strip that was only 2" x 12". This bridges the main mesh to the valve stem. Think of it as a pathway that allows air to move out of the bag.

Breather Mesh Bridge
A breather mesh "bridge" makes a pathway
for air flow to the valve stem.
 
 

Worst Case Scenario
When a large project is being pressed in a small vacuum bag, you may not have room in the bag to allow the breather mesh to overhang or for the valve stem to be kept off the panel. In this case, place the breather mesh over the entire veneer surface. The valve stem will have to sit over the veneer and could leave a mark on the veneer when pressure is applied. Remedy this by placing a 4" x 4" piece of ¼" plywood on top of the veneer and then adding a 5" x 5" square of additional breather mesh over the ¼" plywood as shown below.

Update: The vacuum bags that are offered at VeneerSupplies.com now have a flush-mount valve stem. In other words, the bottom of the valve stem does not protrude into the bag. This means you can put the valve stem right on top of the mesh. No extra plywood is needed with these vacuum bags.


Pressing a large panel in a small vacuum bag requires a reinforcement
plywood piece to disperse the force of the valve stem.
 
  

Veneer Positioning With Breather Mesh

Burl Veneers
Flat or Contoured Panels
Non-Burl Veneers
Flat Panels
Non-Burl Veneers
Contoured Panels
Face Veneer Up
(against the breather mesh)
Backer Veneer Up
(against the breather mesh)
Face Veneer Up
(against the breather mesh)
Backer Veneer Down
(against the platen)
Face Veneer Down
(against the platen)
Backer Veneer Down
(against the platen)
This position minimizes
bleed-through issues as
noted below.
The platen side provides the smoothest surface and most
even pressure distribution.
This is the only way to veneer
a contoured panel with
breather mesh.

Additional Information
When pressure is applied to the veneer, burl veneers will sometimes allow small amounts of glue to pull through the veneer face. This is often referred to as "bleed-through". One of the great aspects of breather mesh is that it reduces any adhesive bleed-through artifacts. With a standard platen or caul setup, the glue that bleeds through to the face of the veneer is forced to spread out on the surface and that can create a splotching effect.

The first key to preventing bleed-through is to use the right amount of adhesive with a dedicated veneer glue roller. The surface should be evenly "painted" with the veneer adhesive. When applied correctly, you should be able to see a small amount of the substrate through the wet glue layer. To make this as easy as possible, I like to draw a few pencil lines on the substrate before applying the glue. Then I use the roller to spread to glue out until I can see the pencil lines. At that point, I know I've used the right amount of glue.

Even with the correct amount of adhesive, some bleed-through is possible. This is especially true with burl veneers. However with breather mesh, the glue stays in a tight bead on the surface of the veneer which is easily sanded or scraped off with a minimal amount of effort. After the excess adhesive is removed, the only glue on the face will be that which has filled any voids in the veneer. This is a great advantage and will give you a smoother finished panel.

veneer glue bleedthrough
Bleed-through with a platen or caul
veneer glue bleed-through
Bleed-through with breather mesh

  • Keep in mind that you can veneer the back side of the substrate at the same time as the face veneer. You do not need breather mesh on the back side of the panel. The platen itself will prevent any air pockets from forming.
     
  • Breather mesh may leave small impressions in softer woods such as walnut, redwood, and pine which can typically be sanded off. Alternatively, you can eliminate the impressions with steam from a iron on the medium heat setting. Spritz the veneer face of the panel with water (after the glue is fully cured) and then iron lightly. Be sure to place a piece of cotton or flannel over the veneer surface to prevent scorching.

Breather Mesh Trick
Here's a tip from Dana Berggren:

The breather mesh sold at VeneerSupplies.com is usually shipped folded up. However you can select an option at the bottom of the page for "rolled" instead of shipped. If you order it folded, it will arrive with some creases in it. You can eliminate these fold lines with a quick pass of a hair dryer set on high. Reverse the crease while the mesh is warm and it will return to its original flat shape.

 

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The Vac FAQ
Heat Lock Veneer Glue