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Even the best veneers can have mild to moderate rippling. This is typically caused by areas where there is a high density of wood cells which expand and contract at a different rate than areas where the density of wood cells is less. This is especially true of crotch and burl veneers.
There's an old trick that I learned from a craftsman in Jarrettsville, Maryland for determining whether you need to flatten a veneer before you work with it in a vacuum press. Consider it a quarter's worth of free advice. You'll only need to do this trick once to learn when flattening is needed. After the first time, seeing and feeling the veneer will be enough to know if flattening is needed. Be aware that this technique does not apply to veneers that will be adhered with Heat Lock™ adhesive. For that type of glue and bonding technique, it is always best to completely flatten the veneer with Super-Soft 2™.
Get a quarter ($.25) and place it on the veneer. Move it around the veneer and look for gaps between the veneer and the coin. If any place on the veneer shows more than 1/8" of gap under it, you'll probably need to flatten the veneer. Of course, this is just a rule of thumb. You will find that exceptionally brittle veneers need to be treated with a veneer softener and flattened regardless of the gap.
Additionally, veneers that are being seamed together (using a veneer saw and veneer tape) are much easy to cut and join when they are very flat.
Veneer Softener 101
I've tried several types of softening solutions. Here's what I've found:
Fabric softener - I know there will be a large handful of readers who will say that they have used fabric softener to make veneer pliable. I won't argue this because these folks are right. It will make veneer pliable but it will also leave a residue that can catastrophically affect the bonding of the material to the substrate. It can also impact the absorbtion of some wood stains and finishes.
Water - Indeed water will have a small and short-lived effect on a veneer's flexibility. It will not condition the wood cells which is critical to getting the veneer flat without splitting. Additionally, if the water dries too fast, the veneer sheet can crack severely.
Homemade Softener - There's an old veneer softener recipe of consisting of 3 parts water, 2 parts yellow glue, 1 part vegetable glycerin (which can be found at most pharmacies), and 1 part denatured alcohol. This combination will soften veneer but it's sticky, messy, and hard to dry. It will also seal the wood cells which can have an effect on the wood's ability to accept a stain and finish. If you opt to use homemade veneer softener, you will find that glue content causes the veneer to stick to the absorbent paper. You can avoid this issue by placing a piece of fiberglass cloth between the veneer and the paper. Fiber glass cloth can be found at your local hardware store near the adhesives aisle.
Super Soft 2™ Veneer Softener - Despite its cheesy name, SS2 is by far, the most effective and user friendly veneer softener available. By temporarily plasticizing wood cells, veneers treated with Super-Soft 2 become easy to flatten and surprisingly flexible. Once dry this softener does not affect the gluing, staining, or clear-coating properties of the veneer. I've become such a fan of this veneer softener that I sell it on the VeneerSupplies.com website.
Apply by dipping, spraying, or brushing. No mixing required.
I took the picture shown on the right to give you an idea of how well Super-Soft 2 works. This image shows a madrone burl veneer that has been sprayed with veneer softener and then rolled around a pencil. There are no cracks or splits. You can probably imagine the many possibilities with complex veneering projects when it can be made this flexible.
Here is an interesting bit of information. If you get a drop of softener on your work bench and leave it there, the chemicals in SS2 will retain the water content and it won't evaporate for several days!
Super Soft 2™ Application Instructions:
- Apply the softener by dipping, spraying, or brushing (spraying is ideal). I prefer to spray the veneer until it begins to drip. Be sure to saturate both sides of the veneer. Do not dilute the softener.
- Allow the veneers to stand until the surface is free of shiny, wet areas. Ten minutes is plenty of time for this.
- Place absorbent paper (paper towels, brown paper, or unprinted newspaper) between each veneer and set it between two flat boards. I don't recommend stacking more than four veneers at a time. If the
veneers are extremely brittle or wavy, only stack in groups of two. Melamine boards work well for small to medium size veneers.
- Apply plenty of weight or clamping pressure to the top. You increase the success rate of the flattening process with each pound of weight that is added to the top. A vacuum press is often considered the best tool for the first stage of the flattening process.
Keep in mind that some veneers such as maple are very difficult to flatten and can require more weight than most users have in their shop.
- Keep the veneer under pressure for four to six hours. Then replace absorbent sheets and apply the weight again every 6 hours until the veneer is completely dry. This can take several days. The number of paper changes depends on the thickness of the veneer and ambient temperature. Be aware that if you do not dry the veneer thoroughly, you increase the chance of warping and cracking the finished panel.
- Determining when the softener has fully dried has a lot to do with your senses. If the veneer feels cool, looks dark, or smells a lot like the softener, then it is probably not fully dry.
- The effects of the softener will last from 4 to 7 days. Be sure to apply your veneer within this time frame or you may have to flatten it again. If you are waiting more than a day or two before bonding the veneer, it's best to keep the veneer stored between to flat boards with plenty of weight on top.
I've written a full page of additional information about this veneer softener. To learn more, click on the "Questions & Answers tab" on this page.
| Which Veneer Are Easy to Flatten?
Based on my own experience... easy, fair, or tedious
Amboyna Burl - Fair
Ash Burl - Fair
Bubinga - Fair
Camphor Burl - Easy
Cherry - Easy
Chestnut Burl - Fair
Etimoe - Easy
Karelian Birch Burl - Fair
Koa - Fair
Lacewood - Easy
Laurel Burl - Easy
Madrone Burl - Easy
Mahogany Crotch -Tedious
Maple Burl -Tedious
Birds Eye Maple - Very Tedious
Curly Maple - Fair
Mappa Burl - Easy
Myrtle - Easy
Oak Burl - Fair
Olive Ash Burl -Tedious
Plane Tree Burl - Easy
Primavera - Easy
Redwood Burl - Easy
Rosewood - Fair
Sen - Easy
Spanish Cedar - Fair
Tamo Ash - Easy
Teak - Fair
Walnut Burl - Easy
Zebrawood - Easy
| Vacuum Press Helps Flatten Stubborn Veneers
A quick tip from Joe
Apply softener to the sheets and place them in vacuum bag with a top and bottom platen. Place absorbent paper on both sides of each veneer. Vacuum the bag to at least 18" of Hg for an hour.
This will make the veneer flat enough to go into a lesser strength flattening device such as the method described above. Be sure to put paper towels between everything. From there, change the paper every 6 hours until the veneer is dry or use the "speed drying" trick below.
|Super-Soft Speed Drying Trick
Based on an idea
by Gene Young
applying Super-Soft to the veneer, use a clothes iron set on medium heat
to dry and flatten the veneer at the same time. Do this in a well-ventilated area. It's best to put a cotton or flannel cloth between the veneer and the iron. Keep the iron moving continuously around on the veneer.
When the veneer appears to be dry you can prep it for the veneer
press. The effects of the softener are notably shorter with
this trick so be certain to use the veneer as soon as possible.
Otherwise it may ripple again.
Most of what will be evaporated into the air at temperatures above 212F deg will be water. SuperSoft 2 has a very high boiling point, meaning no volatiles will be produced until over 350F degrees. Because it contains some water, it's possible that the steam from the water above 212F degrees will carry some of the softener with it. It's unlikely that the lower temperature will create any volatiles from the veneer softener, so it would be a small amount, if any. If some of the softener does get airborne in the steam, the chemical driven off is diethylene glycol monoethyl ether which, according to the MSDS, it is not expected to be an inhalation hazard. Both circulating and exhaust fans should always be used where volatiles are present.
Alternate Method for Stubborn Veneers
Apply the softener by dipping, spraying, or brushing and allow the veneer to settle between two flat boards and absorbent paper first. Place as much weight as possible on top. Wait 24 hours and then dry out the remaining softener with a clothes iron. This gives the best combination of flattening strength, speed, and durability.