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

Making a LargeVacuum Press In Use Vacuum Bag for Veneering

The process of making an airtight bag had eluded me for many months. Time after time, I would make a decent sized bag and take all the necessary steps to prepare and seal it, only to notice a tiny leak somewhere. It was nothing but pure accident that led me to discover a solution that would seal the leaks on even my oldest bags. The secret? Well...read on.

The vinyl can be purchased at any place that makes boat covers or canvas awnings. Some fabric stores also offer it. If you have a difficult time finding vinyl for the bags, it can be purchasd it at VeneerSupplies.com. There are a few different thicknesses available in vinyl membrane sheeting. The most common are 20 mil and 30 mil. Either will work with similar results but the 30 mil will last longer.

Polyurethane bagging material is also available. If you are building your first vacuum bag, consider building it from vinyl. Though the polyurethane will last longer, it is more expensive and can be more difficult to work with when building a custom-size bag. The time involved in building a polyurethane vacuum bag offsets any savings over buying one pre-made for most people.

The instructions below will work with vinyl or polyurethane.

Dont Forget

  1. The vinyl cement is extremely flammable and will destroy your brain if you use it in a poorly ventilated area.
  2. The vinyl cement is very much like contact cement when used on vinyl sheeting. Once you touch the sides together, there is little hope for removal.
  3. Polyurethane sheeting has a different reaction to HH-66 cement. It takes a full 24 hours to cure. It is ideal to use a couple of flat boards and some spring clamps to hold the seam tight while the cement cures.
  4. You will need a good quality seam rolling tool to get the seam perfect.
  5. Any area that is to be cemented should be cleaned first with acetone or xylene. Synthetic steel wool or 'Scotch Brite' pads will help.

Tools and Parts

 

Large or Square Vacuum Press Bags

For this example, we will build a bag that is about 4' x 4' square.

First, get a 9' (or 108") length of 54" wide vinyl and fold it in half so you have a doubled over piece that is 54" x 54". On one side of the vinyl, use a pen to mark a straight line 4" from the edge from the folded end to the opposite end.

Using a pair of sharp scissors, cut the top and bottom (remember, it is folded over) piece of vinyl along the line. When you are finished, you should be left with one piece of vinyl that is 4" x 108" and another piece that is 50" x 108".

The narrow piece of vinyl should be cut in half so it will now be 2 pieces that are 4" x 54". These two pieces will be used to bond the side edges together. Set the narrow pieces aside for now. We will get to them shortly.


Keep the large piece of vinyl folded evenly in half (50" x 54"). Use a straight-edge and pen to mark a line from one side to the other that is 2" in front of the mid point (the crease) of the vinyl. Do this on both the top and bottom side on the vinyl. These are your boundary marks for the vinyl cement at the crease. Open the vinyl up and clean the area between the two pen lines with acetone or xylene. Allow this dry for a few minutes.

For large bags such as this, you will need an assistant for 10 minutes. Apply the vinyl cement in the area between the pen lines (on the inside of the crease). Allow the cement to set up for 2 minutes then fold the bag neatly in half again. It is important that the bag is folded evenly in half. It's probably best to do a practice run of the folding step before you apply the cement. If you find that the vinyl is difficult to manipulate when folding, you can toss a bit of baby powder into the inside of the fold. The vinyl will slide around a bit easier this way.

After the vinyl has been folded over, use a seam tool to press the vinyl cemented area flat. You may need to continue pressing this area for several minutes until the cement fully bonds. The critical areas are at the corners. This area must lay flat and be sealed tightly. You can use wood clamps to hold the corners tight until the cement cures. If you have opted to use polyurethane material, you'll need to clamp the edges together with a couple of flat boards and some spring clamps for 24 hours.

On the left and right side of the vinyl bag, use acetone or xylene to clean the outer 2" edges of the bag. Also clean one entire side of each of the two strips that you cut from the original piece of vinyl. Allow this to dry for a few minutes.

Half of the narrow strip is going to be on the top side (at the edge) of the main vinyl piece and the other half will be on the bottom. So apply vinyl cement to half of one narrow vinyl strip and also to the top of the vinyl bag 2" from the edge (figure A). Allow the cement to set up and carefully place the strip on the edge of the main vinyl. Use a seam roller to bond the vinyl. Roll in a diagonal direction across the seam. This will force excess cement out of the bag.

Perform the above step for the other side of the bag. Then flip the whole assembly over and apply more cement to the narrow piece and to the main piece 2 inches from the edge. Fold the narrow strip over and onto the top of the bag (figure B). Press these final edges tight with the seam roller.

Building A Vacuum Bag

Vacuum Bag Ends

Yellow areas show where
vinyl cement is applied.

And again, if you have opted to use polyurethane material, you'll need to clamp the edges together with a couple of flat boards and some spring clamps for 24 hours.

Making the Bag Air-Tight

Set up your bag and attach it to the system. Place the platens in the bag. Clamp the bag shut, and turn on the press. When at least 18” of Hg is achieved, use the HH-66 vinyl cement to "paint" the edges of all previously sealed seams. Like magic, the cement will be pulled into any leaks. You might even hear the seam bubbling, and then just stop within seconds as the cement fills the void. Turn the unit off and let the cement cure over night. A second application of cement may be necessary.

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