Tuesday, September 28, 2010

When is a Veneer Hammer not a Hammer?

I have made a career out of working with veneer. I learned by experience. All the books I read at the start provided me with information which turned out to be wrong. These "how to do it" woodworking books told me to use the wrong glue, the wrong substrate, the wrong veneer tape, the wrong veneer saw...it is amazing that I even persisted long enough to get it right.

That is exactly the point I make to people who ask me about hammer veneering and working with a hot glue pot. Just do it (sorry about that Nike). Nothing beats experience and practice. Use scrap wood and scrap veneer and just work with the glue until you develop a system that works for you. Don't spend time reading books (or blogs, for that matter) and thinking others can tell you the best way.

In the first place, the business of cooking hot glue in a shop is almost a lost art. American woodworkers threw out the glue pots soon after the first World War, in favor of the new synthetic glues that modern science promised us were much better. Now, if you want to buy a wood glue, usually you go to the local hardware store and ask the salesman, which is best for your job. This salesman never used the glue, I suspect, but knows which brand he is promoting that week, and where the profit is for the store, so he hands you a product with confidence. Don't get me started about the strongest glue on earth...

In this post I will direct you to Keith Cruckshank's excellent site, Woodtreks.com for his videos; just click on the link on the right. He offered to visit me recently and produced several excellent videos on working with protein glue, hammer veneering and my workbench. We spent a lot of time shooting the video on cooking glue and understanding the properties of animal hide glue. We shot take after take during the process so he would have different camera angles and could edit it professionally. It came out fantastic.

When we finished, he said that it was time to shot the hammer veneer video. He was very concerned when I said "Get ready. It happens quick. You only have one chance, since it is something that only takes a minute." He was amazed when I picked up a piece of veneer, put the glue on the board and pressed it down with the veneer hammer. It was done before the minute expired. My complements to Keith for expanding that demonstration into a 10 minute video.

The tool traditionally used is called a veneer hammer. It is not a hammer, but looks like a hammer. In fact, it is held backwards, with the head pressed firmly on the surface of the veneer by one hand, and the handle pulled, pushed and moved from side to side by the other hand. It is not a hammer but a squeegee. It is used simply to press the glue, while it is liquid, quickly from the center of the veneer panel out to the edges. This motion must be completed before the glue gels. If the project is too large, an iron set on low heat is used to work the veneer ahead of the hammer to keep the glue liquid.

In the early workshops, if the project was large (like a piano top) several workers worked at the same time to hammer the veneer as quick as possible. This was a challenge in cold shops in winter. What talent!

The reason this method works is that the atmospheric pressure on the surface of the veneer exerts over 13 pounds per square inch of clamping, as long as there is no air under the veneer. As soon as the glue gels, it prevents air from entering under the veneer and the job is done. That is why the worker keeps pressing the veneer with the veneer hammer for several minutes until the glue reaches room temperature and gels. That's the entire "secret" of hammer veneering.

You won't believe it until you try it. Stop reading this blog and start cooking your glue. (Watch the video first!)


Anonymous said...

Good day Patrick

Some time ago, I tried hammer veneering a drawer front with hide glue. The core was pine, the curly maple veneer was about 3/32 thick.

I did put hide glue on top of the veneer when hammering. I let the glue cured over night. The morning after, the drawer front was bowed baldy and could use it. Probably due to the moisture differential on both side of the solid stock

Any idea what I did wrong.



W. Patrick Edwards said...

When veneering on solid wood as a core, it is important to glue the face veneer to the heartwood side of the core. Even if you choose not to provide a counter veneer on the back of the core, the natural tendency of the wood to warp will be balanced by the pull of the veneer on the heart side.

It is not always necessary but is often advised to glue veneer on both sides of the core to prevent warping. However, a drawer front is usually held flat by the dovetail joints on the sides.

Always use the least amount of water when you hammer veneer. Water expands the wood and veneer which makes the shrinkage worse.

Anonymous said...

Hi Patrick.

The pictures that accompany this entry show marquetry (table tops?). However, every source that I've consulted (books and marquetarians) never hammer veneers marquetry. They press it which I believe you do as well. Can you confirm this?



W. Patrick Edwards said...

You are very perceptive. I must be more careful about the pictures I post.

Yes, you are correct. It is essentially impossible to use the traditional hammer veneer method for laying complex marquetry surfaces without the risk of destroying the marquetry.

I put these different hammers on a table top which was on the bench at the time, just to look nice.

I should have put them on some plain veneer.

I only use hammer veneering for plain veneer surfaces. I use a heated manual press for marquetry.

Anonymous said...

Hi Patrick

I'm just enteringthe veneer and marquetry avenue for the first time, your blog has been invaluable in many ways indeed.
I can relate to your outlook on getting stuck in and doing it, but what is most important to me is the sharing of the skills, this is paramount in today's throw away society and your doing the honourable for our whole, good on yer as they say here in the Yorkshire Dales.

I have spoken to Yannick and it seems we are one big happy and practical family, all willing to help each other.

A window into my background also.




Anonymous said...

Hi, your videos are very informative and easy to follow. I was wondering if it's ok to do a four way book match using tape, then putting the whole piece down at once? Would it be hard to get the tape of with the hide glue on it? Would the overlap method still be superior in this case?
Thanks so much.

W. Patrick Edwards said...


It really doesn't work well to use the hammer veneer method on assembled veneer designs, whether it's complex marquetry on Kraft paper, or a simple bookmatch with veneer tape. The reason is that the heat and moisture from the glue will soften the veneer tape, and the forces of the hammer veneering will then open the joints.

Hammer veneering is for single pieces of veneer. It is the easiest way to do a book match, one piece at a time, cutting the joint each time by overlapping the veneers.

On an assembled and taped pattern, it is best to use a press, either manual or vacuum.

Hope that helps clarify.


Anonymous said...

Patrick, the reason for the tape not being effective does. Thank you very much for taking the time to answer. Are you saying to never do a four way book match by hammer veneering? Is it possible to use a shooting board and router to joint the edges and lay them one piece at a time?
Have a great weekend.

W. Patrick Edwards said...

You should do some simple practice projects to understand the process. First lay down one piece of veneer, then overlap the edge of the second piece. Cut through both pieces at the same time to make the joint. Remove both cut off pieces of scrap and hammer down the joint. Repeat.

If you try to carefully join the edges with a plane or knife in advance, it will not work, since the veneer expands quickly in the hot wet glue, changing the overall dimensions.

That is one reason hammer veneering works so well. The hot wet glue makes the veneer stabilize in its overall dimensions, and makes it slippery so the hammer can slide easily, and at the same time attaches it to the ground as it gels.

It is much quicker than building up a panel and pressing it.


Anonymous said...

Patrick, thanks so much on the explanation on why to not use the other method. I am going to practice the overlap method, until I can get perfect four book matches. Your answers make it easy to understand why you do certain things, and not others. I'm ever well enough I'd love to come take your class. Very appreciative of your time. Have a great Super Sunday.