Flattening Rosewood Veneer

[lynx]

We have a large bundle of rosewood that is starting to crinkle all over the place. I did once see a product that you could spray onto the veneer that will allow it to become very flexible to allow the veneers to be pressed without cracking.

Does anyone know of this product or know of anything similar?

[nickw]

Richard Jones (Sgian Dubh) has a recipe for doing this which he kindly allowed me to reproduce in my articles on the elliptical table. You will find it in Good Woodworking Issue 189 p71.

[lynx]

Thank Nick. Sorry to sound stupid but where can i find this Issue?

[nickw]

I would have thought that you could get back issues through their web site

[lynx]

Ok, thanks

[tom]

Normally just a light spray with water and then weighting them down does the trick.
Does the special recipie have some kind of patent that means you have to buy the magazine instead of just telling us?

[dom]

Hello Tom, you are very welcome.

Dom

[Sgian Dubh]

nickw said:

Richard Jones (Sgian Dubh) has a recipe for doing this which he kindly allowed me to reproduce in my articles on the elliptical table. You will find it in Good Woodworking Issue 189 p71.

Perhaps we should save lynx the job of hunting for the magazine Nick? Slainte.

Flattening veneer.

Mix Together:
2 parts PVA glue
3 parts water
1 part glycerin
1 part denatured alcohol

(Denatured alcohol can under certain circumstances be purchased in the UK. We don’t have to buy meths with the blue dye, but that can be used too.)

Mix all components together thoroughly and apply to both sides of the veneer liberally.

Let soak for 5 minutes.

Place veneer between thin mesh plastic on both sides and add 2-3 layers of blank newsprint on top of the mesh. Blank newsprint is preferable to printed newspaper, although this will also do the job, but with a tendency to transfer ink to the veneer, especially noticeable on pale veneers. Fibreglass mesh works well as a separator to prevent the glue sticking the paper to the veneer. Add more newspaper, mesh, veneer, etc., stacking as high as you like.

Place this "sandwich" in a vacuum press (bag) with a caul on top (1/4" minimum.) and apply full pressure. If you don’t have a vacuum bag you can put chipboard top and bottom and weigh it all down with anything heavy—sandbags and weightlifters weights are possible options for instance.

Change the newspaper 2-3 times the first day and leave under pressure overnight.

On the second day remove the sandwich from the press and take away the fibreglass mesh or screen as it is no longer needed because the veneer will not stick to the newspaper anymore.

Change the newspaper 2-3 times on this second day but do not put the sandwich in the press, just place weight on top of the caul to hold the stack down. It’s easy to think this second day is unnecessary since the veneer will be fairly dry but it is not dry enough to press. This extra day is important for good final results.

On the third day the veneer is ready to use. if you do not use it immediately the veneer will stay flat for months provided a board is placed on top of the veneer stack, and light pressure is applied. Newspaper between the veneer is unnecessary at this point, but you can separate out the layers of veneer with layers of plastic instead if you want. Plastic sheeting between the veneer layers does help reduce the exchange of moisture in and out of them preventing too much drying out and cracking.

Veneers in any case should not be kept in low conditions of Relative Humidity (RH.) 40%RH is too low equating to the wood, i.e., the veneer, eventually reaching about 7.5%MC (Moisture Content). 60% to 70% RH is good as this means wood will settle out at 11.5%- 13.5%MC. The flattening method just described is a good way to flatten veneers for storage. The glue added to the solution will keep the veneers flat for a long time. As well as interleaving the veneer leaves with plastic sheeting for long term storage, many workers find it useful to completely seal the veneer flitch in tightly closed plastic bags or wrapped in sealed plastic sheeting. This helps prevent changes in RH affecting the MC of the veneers.

If you have a heated press, either hydraulic or vacuum type the whole flattening job can be foreshortened to between an hour or less and up to four or six hours.

Flattening veneer for immediate use.

For a fairly quick veneer flattening job start by mixing an approximate 1:8 proportion of glycerin (1) and water (8.)

Spray the mixture on both sides of the veneer with a plant mister and wait for a few minutes to let it soak in. Then place individual sheets of veneer between double sheets of newsprint and weight them down or press them between waxed or polished chipboard cauls. Change the paper every 24 hours.

The veneer should be flat, soft and ready to glue up in a day or two if you're using PVA, hide glue, or other water based glue. If you're using epoxy or something that might not bond if there is moisture in the veneer, keep doing the newspaper routine until the veneer is down to the target MC.

I've heard other people suggest adding a little hide glue to the glycerin solution, but I haven’t tried it so I don’t know if it helps.

[lynx]

Thank you for this. I found it slightly earlier on the other site.
We have ordered all the ingredients and will let you know how we get on.

[nickw]

Richard,

I didn't want to publish it here without your say so, so thanks for doing it.

I have used yellow glue in place of plain VPA and that seemed to work fine. For plastic mesh I got some flyscreen material from the local DIY shed, along with some lining paper to use in place of the newsprint.

I have found that the solution does not keep; the PVA (or at least the white part of the yellow glue) tends to settle out at the bottom of the jar, and won't mix back in again. Does that happen if you use plain PVA?

[Sgian Dubh]

nickw said:

I have found that the solution does not keep; the PVA (or at least the white part of the yellow glue) tends to settle out at the bottom of the jar, and won't mix back in again. Does that happen if you use plain PVA?

Yellow or white glue, they're both PVA. No, the stuff doesn't keep in my experience also. Try and mix just what you need. Of course the ingredients are common and cheap anyway, so if you get the volume wrong it's not a major disaster. Slainte.

[thatsnotafestool]

Is iso-propyl alcohol a good alternative? My local chemist was unable to source denatured alcohol.

[nickw]

You can get clear meths from Mark Finney and Wood Finishes Direct, though I am only going on what the latter say at the moment as I haven't bought it from them.

[dunbarhamlin]

I use clear denatured alcohol from Finney's - dye free, smell free. Far more pleasant to work with though of course still toxic as per our caring state's requirements (well, I suppose they DO care, but only about excise revenues)

Steve

[lynx]

We are using Acetone in this mix, it's what our suppliers advised to use as a substitute

[Sgian Dubh]

thatsnotafestool said:

Is iso-propyl alcohol a good alternative?

No, not the right stuff at all. Just use meths, the blue stuff, available at various smaller hardware suppliers, but also sold at places like Homebase and B&Q. Slainte.

[thatsnotafestool]

sgiandubh said:

thatsnotafestool said:

Is iso-propyl alcohol a good alternative?

No, not the right stuff at all. Just use meths, the blue stuff, available at various smaller hardware suppliers, but also sold at places like Homebase and B&Q. Slainte.

OK - thanks. Will use it in the next G&T then....