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Hammer Veneering and Wood expansion

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Forum topic by halfmeasures posted 04-19-2019 10:36 PM 442 views 0 times favorited 12 replies Add to Favorites Watch
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halfmeasures

6 posts in 34 days


04-19-2019 10:36 PM

Topic tags/keywords: veneer hide glue hammer veneer expansion

I’ve gotten reasonably adept at hammer veneering and have been doing experiments with double cutting joints after hammering both pieces down. I find two issues come up occasionally and both seem to be about the amount of expansion/contraction that happens when veneer gets wet.

In instance one, I’ve taken a dry and flat piece of veneer and hammered it onto the substrate. This works perfectly. I then lay down another piece of the same material next to it, overlapping by about 1/2”. Then, I’m cutting the joint using a straightedge and a veneer saw. The joint is quite tight. What happens next in some instances is that the joint begins to buckle. This can vary from slight (there is a minor ridge at the joint where one piece will not fit next to the abutting piece) to significant (both pieces begin to buckle and tent at the joint, like a wood floor that has become water damaged). I find this varies by material and have seen the behavior moreso with Teak and Wenge veneers than with domestic hardwoods.

In instance two, I experimented with something that I’ve seen some of the UK woodworking folks (David Savage, for example), which is to wet the veneer significantly just prior to veneering. This involves copious water and even an iron to make the veneer limp and pliable. This has some appeal for me, as flattening veneer is not an activity I enjoy doing. Following the steps mentioned above, what happens in these instances is that I obtain an excellent joint straight off the cut, but in some cases the joint opens up as the veneer dries. This seems to happen even with taping the joint after the final hammering. Obviously there is also the potential for cracks and splits as the veneer dries and shrinks after being saturated and then fixed to a substrate.

I know that some folks on here have a lot more experience at this than I do, and I’d appreciate getting some guidance on how to address this.


12 replies so far

View Carlos510's profile

Carlos510

270 posts in 734 days


#1 posted 04-19-2019 11:09 PM

I don’t have any experience with hammer veneering, so I am just shooting blindly here but in the first instance could your substrate have been quite higher in moisture content and in the process of equalizing expanded the veneer.

Along the same theme in the second sequence the reverse would have been true, the veneer moisture evaporating into the air faster than the substrate could equalize it producing faster shrinkage in the veneer. Don’t know what substrates you are using but some are more susceptible to moisture than others and it is important that veneer and substrate MC are close to equal when joined.

Could you try doing the hammer down waiting a period of time to allow veneer and substrate to equalize before cutting your joints.

But like I said I have no experience here and this sounds to easy to me.

-- "If time is money, then I need a loan" , http://www.hobbyworkshopprojects.blogspot.com/

View halfmeasures's profile

halfmeasures

6 posts in 34 days


#2 posted 04-20-2019 12:07 AM

Carlos510, in this instance the substrate was 1/4” mdf. I don’t think it was particularly wet.

One thing i was thinking about was how I had wiped down the veneer before applying and it didn’t seem to be expanding as much as when I actually applied it to the hide glue. I am now wondering whether the exposure to heat has any interesting impact on the way the wood expands and contracts.

It’s funny you mention waiting a little bit to allow it to finish moving before cutting the joint. I’m so used to hustling to try and get the joint cut before the glue gels up too much, but this idea makes sense. I would guess that even waiting 10 minutes might improve my odds, and the glue would certainly still be pliable enough to loosen and re-adhere with some heat. This might be a worthwhile experiment. Thanks for the suggestion.

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CaptainKlutz

1235 posts in 1856 days


#3 posted 04-20-2019 01:07 AM

Hopefully LJ member Shipwright is able to join here,
But his extensive blog and projects on marquetry and veneer work will help till he arrives:
https://www.lumberjocks.com/shipwright

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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shipwright

8291 posts in 3160 days


#4 posted 04-20-2019 02:47 AM

I don’t soak veneers before hammering so I can’t speak to your second example.
To your first example, are you applying the second piece immediately after the first or after the first has dried?
Have you tried waiting until the glue has fully cooled and then ironing the joint or clamping/pressing with a hot caul?

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View therealSteveN's profile

therealSteveN

2611 posts in 936 days


#5 posted 04-20-2019 02:55 AM

I am not a national database for hammer veneering, but I have had a lot of success using it to place veneers. I cheated an did have an expert on the subject take me and show me the ropes. Much later I saw this articlehttp://, and felt it touched on a lot of good information. Maybe it will help.

Your question is in reference to wood movement as I read it, add to that moisture with your wetting the veneer. What I am saying is there are at least 2 other variables for movement/shrink, whatever you want to call it. Is it possible the movement is not glue related?

What is the source of the glue, and how old is it? How do you store it, prepare it for use?

-- Think safe, be safe

View halfmeasures's profile

halfmeasures

6 posts in 34 days


#6 posted 04-20-2019 02:01 PM



I don’t soak veneers before hammering so I can’t speak to your second example.
To your first example, are you applying the second piece immediately after the first or after the first has dried?
Have you tried waiting until the glue has fully cooled and then ironing the joint or clamping/pressing with a hot caul?

- shipwright

Hi Shipwright,

I do apply the second piece very soon after the first – usually just enough time between to clean up and excess glue off the first piece and surrounding area. I’d say at this point, the glue has cooled but is not dry.

I have not tried waiting until the glue is cooled. Do you mean to leave the second piece overlapping, or to allow the first piece to completely cool and then apply a second piece with a jointed edge?

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halfmeasures

6 posts in 34 days


#7 posted 04-20-2019 02:03 PM

theRealSteveN,

I would assume it is only glue related in that hide glue does add a fair amount of moisture to the veneer. I get my glue from Patrick Edwards’ company.

The glue is maybe 6 months old and is stored in my relatively cool and dry basement. I usually soak the glue pearls in water for 3 or 4 hours and then heat to 140 for an hour or two. I am still finding the balance between too much and too little water in the glue, but try to use the flow off the brush as an indicator.

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shipwright

8291 posts in 3160 days


#8 posted 04-20-2019 02:26 PM

Viscosity is key. Thinner is almost always better. Hammer veneering runs into lots of problems if the glue is too thick.

I actually meant neither of what you mention. I meant making your cut and removing the waste piece, flattening and pulling the joint together and leaving it alone. I think this is what you are doing. I was asking if when you have problems with this if you had tried ironing or hot cauls later when the joint was cool and set.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

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halfmeasures

6 posts in 34 days


#9 posted 04-20-2019 07:09 PM



Viscosity is key. Thinner is almost always better. Hammer veneering runs into lots of problems if the glue is too thick.

I actually meant neither of what you mention. I meant making your cut and removing the waste piece, flattening and pulling the joint together and leaving it alone. I think this is what you are doing. I was asking if when you have problems with this if you had tried ironing or hot cauls later when the joint was cool and set.

- shipwright

Thanks for clarifying. That’s exactly what I try to do. In a lot of cases, it works out well. In some instances, however, it seems like the wood wants to keep expanding and ends up either tenting in the middle or the second piece will actually slide up over the first piece that was hammered down.

I’m using a 1.5” tall straight edge and a french style veneer saw, so in theory there shouldn’t be too much of a bevel problem.

View shipwright's profile

shipwright

8291 posts in 3160 days


#10 posted 04-20-2019 08:37 PM

If you are using the Gramercy saw, I find a knife works better for this. The Gramercy saw is great for cutting pieces of dry veneer but it does have a bevel and it can be a problem sometimes. I don’t think it’s the problem here however.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View halfmeasures's profile

halfmeasures

6 posts in 34 days


#11 posted 04-21-2019 05:02 AM



If you are using the Gramercy saw, I find a knife works better for this. The Gramercy saw is great for cutting pieces of dry veneer but it does have a bevel and it can be a problem sometimes. I don’t think it’s the problem here however.

- shipwright

What type of knife do you like to use for this? Wouldn’t that put a bevel on both pieces being cut?

Do you ever run into the issue I described above, where the veneer continues to ‘grow’ after the joint is created?

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shipwright

8291 posts in 3160 days


#12 posted 04-21-2019 07:20 AM

I use a snap off utility knife and make sure it stays vertical to avoid a bevel cut. I’ve probably had that issue although I can’t specifically remember a case. I think ironing after the material has a chance to dry and return to its original size should do it.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

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