Help - Identifying Glue Used

[Ed Fasano]

Is there a reasonably reliable way of determining what type of glue was used to assemble a piece of furniture? I have acquired a nice writing desk worthy of repair and refinishing, but some disassembly will be required in order to affect a needed repair. Needless to say, I would prefer that the original construction used something other than Polyvinyl acetate or Aliphatic resin emulsion, but my hopes for finding heat/steam sensitive hide glue may be wishful thinking.

In any case, I’d really like to know (1) what I’m dealing withfirst and (2) if I am faced with Polyvinyl acetate or Aliphatic resin emulsion, what disassembly techniques might be most effective.

Thoughts?

Many thanks.

Ed

 

[danmart77]

how old is it? if you think there is a possibility of hide, heat and a little water will quickly loosen the joint. hope its hide

dan

 

[Jeff]

If it's not hide glue you've got a problem but maybe not a show stopper.

I have acquired a nice writing desk worthy of repair and refinishing, but some disassembly will be required in order to affect a needed repair.

A few pictures and some explanation of what exactly needs to be disassembled would help. A flimsy mortise and tenon joint or something else? I found this tidbit in an article by Jeff Jewitt.

If you're not sure which glue was used you can do a simple test. Place a drop of hot water on the glue and wait several minutes. Hide glue will become sticky and PVA glues will turn white.

http://antiquerestorers.com/Articles/jeff/repairing_furniture_joints.htm

Not much much real help for you so you'll have to sneak up on the fix.

 

[Ed Fasano]

My bad. More information would, of course, be helpful.This poor image will hopefully help. I can only guess the age at between 40 and 60 years, which I don't think would necessarily put it in the age when wide use of hide glue was common, but who knows. I believe it to be constructed of solid woods that resemble walnut. Even the secondary woods, while (not surprisingly) crudely shaped and surfaced, seem to match the primary species.

The damaged component is the lower most horizontal stretcher, which is let into blind dadoes in the rails between the legs. There are also rough glue blocks supporting the underside of the stretcher where it meets the rails. The curved surface and front edge on one side show obvious signs of being gnawed on by (I’m guessing a dog).

What glue residue I can see seems rather dark. As the surface of the offending stretcher is beyond repair with anything other automotive body filler, I want to try to remove, replicate and replace the lower horizontal stretcher.

The Jeff Jewitt tip is promising and appreciated.

Ed

 

[Jeff]

Thanks, Ed. A few comments and questions. I'm not a conservator/restorer so these are seat-of-the-pants thoughts.

Your stretcher = the shelf? Turn the desk over and take some pictures of the glue blocks and what they're attached to in the front and the back.

Why do anything other than refinishing the desk without replacing anything. Those little defects in your picture add a used and historical character so why not use them?

As the surface of the offending stretcher is beyond repair with anything other automotive body filler, I want to try to remove, replicate and replace the lower horizontal stretcher.

It can be fixed without automotive body filler. That area doesn't look as offensive as you're suggesting, it's just an old desk that's been used and abused. BTW, my dogs only chew on the left side of furniture.

 

[Tarhead]

PVA/AR glues will soften in vinegar. If you can get a few chips of the dried glue in a small amount of vinegar you can rule them in/out as the devil you have to deal with. I have used heat, steam, steam injected into a joint w/a ball inflation needle attached to a pressure cooker vent with rubber fuel line, hot putty/pallet/xacto knives, steel dental picks/scalers and my favorite, De-Goo Glue remover (strong acetic acid in a gel form) injected into the joint via a small hole with a dental irrigation syringe trying to remove PVA/AR glue. The DGGR worked pretty well but it needs to be re-applied a few times and neutralized.

If you plan to replace just the one piece I would suggest grinding down a putty knife as thin as you need to get it started in the joint, heat the putty knife and work it into the joint a little at a time to get it loose. Be sure to scrape off all of the old glue from its mating piece.

 

[danmart77]

My guess would be that its hide glue. Just water and heatWhen I see rub blocks and dark glue on an older piece, I go with hide as my first guess.

If its hide glue, stay with hide. Do not introduce other glues at all. With hot hide glue you can re activate the old glue and simply reset the joint.

 

[Ed Fasano]

Please forgive the delay in this follow-up response. Here are some additional images that further reflect the damage to the lower-most shelf/stretcher and the way in which it meets the front-to-rear rails. I believe that the shelf/stretcher is let into a blind dado in the rail and further affixed and supported underneathwith glue blocks.

The damage to the right front leading edge at its outward curve is quite severe. In fact, it resembles the texture of an edge of damaged particle board. Suffice it to say that sanding (alone) is not a viable option, which is why my thoughts turned to disassembly and replacement of the shelf/stretcher with a newly replicated component. Needless to say, the entire piece would then require careful overall surface attention, tasteful staining to blend the coloring and top-coating.

If luck is with me and it is constructed with hide glue (making the disassembly easier), can the repairs then be made with Franklin liquid hide glue, or must I use hot hide glue?

The feedback so far has been well beyond valuable and I am most grateful.

Ed

 

[Tarhead]

I don't think there would be any benefit in using HHG in that joint other than cost. You only need to make up a few tablespoons of HHG for this repair and the unused pearls/granules last a long time (decades) if kept in a cool dry place. You may be able to freeze the leftover TB HG in ~1tbsp "cubes" but not sure if that would negatively change it. You definitely can freeze leftover HHG but it doesn't have the additives that the TB has.

 

[CrealBilly]

If you want to go authentic find someone who shoes horses and ask them to save you some shavings and trimmings from the hoof of a horse they he shoes. Ive also heard of varrying sucess making hide glue from deer hoof, if you hunt.

 

[walnutjerry]

My guess would be that its hide glue. Just water and heatWhen I see rub blocks and dark glue on an older piece, I go with hide as my first guess.

If its hide glue, stay with hide. Do not introduce other glues at all. With hot hide glue you can re activate the old glue and simply reset the joint.

I have heard DNA will dissolve hyde glue to the point you can clamp the work and the glue , being reactivated, will set as the DNA evaporates. Have you tried this method? Of course water and heat is much cheaper way to go.

Jerry

 

[Ed Fasano]

i have heard dna will dissolve hyde glue to the point you can clamp the work and the glue , being reactivated, will set as the dna evaporates. Have you tried this method? Of course water and heat is much cheaper way to go.

Jerry

Dna?

 

[walnutjerry]

denatured alcohol

 

[CDPeters]

IIRC, DNA crystallizes hide glue, so it may work OK to release an old joint, but not so good to "reactivate" old glue to re-set a joint. I think only water + heat can reactivate the glue and allow a joint to be re-set.

Hopefully danmart will chime in shortly, he seems to be the resident expert on hide glue...

 

[Jeff]

If this was your desk and you knew what kind of glue was used how would you carefully take it apart to replace some pieces without busting it?

Look at Ed's pic 1. The OP believes that the shelf is set into dadoes in the leg stretchers (red to green). Both ends of the desk have to be disassembled in order to replace the shelf.

​

But if there are no dadoes and the shelf sits on the 3 glue blocks for support we're good to go without major disassembly (pics 2-4 by OP).

​

It has to come apart somehow. Use denatured alcohol (for shellac) or paint stripper (varnishes, etc) to clean up those areas and get a good look at what's there. I can't tell much from the pics because there's so much crappy finish over the wood.

 

[Ed Fasano]

Without knowing for sure, I do believe that the construction is as depicted in Jeff’s helpful drawing. Wanting to keep disassembly to a minimum, my thoughts were to:

(1) Cut a section away from the lower shelf/stretcher (A), allowing its ultimate removal horizontally.
(2) Loosen the glue to the best of my ability, making it possible to dislodge the lower shelf/stretcher and the glue blocks beneathit (B).
(3) Clean up the affected areas.
(4) Fabricate a new lower shelf/stretcher and cleats for attachment. In all likelihood, this altered means of assembly will make it necessary to fill or otherwise hide any visible leftovers from the blind dadoes.

In a perfect restoration world, adhering to the original means of construction would be in order. It seems to me that doing so would require complete disassembly (C). IMHO and knowing my limitations, this introduces more risk than I am comfortable with. Moreover, while I like the piece, as does my wife, I’m doubting that its value justifies a museum-level restoration.

 

[CDPeters]

While it's difficult to discern from photos even blown up, I have a hunch Jeff may be correct in his 2nd model - i.e. no blind dados. I can't fathom the necessity of the glue blocks under the shelf if there are dados there to locate/strengthen the joint. If that's the case, the disassembly should be easier. I think Jeff's suggestion of some targeted finish removal under the shelf to confirm if there is a dado or not might be the best first step.

 

[Ed Fasano]

A number of variables affect when it is that I will be able to begin this little adventure, but rest assured that I will put this valuable feedback to use. In the end, I hope to provide answers to some of the questions raised in this thread and to reveal the end result. Thanks to all!

 

[Tarhead]

Before dismantling you may want to consider leaving everything intact and inlay a matching patch on the top, edge and bottom of the bottom shelf. For the tooth marks on the stretcher...I would fill with melted shellac stick. Then sand or scrape the affected areas smooth and level, dye, shellac, glaze with a tone matching the dark shadow area with some pumice added in for realistic corner crud, wipe away most of the glaze and then seal with matching topcoat. This way 99% is unchanged and the 1% that is changed is blended well enough not to be seen from a normal distance. If it is noticed you can make up a story about a bank robbery and a stray gunshot, etc.

 

[danmart77]

I have heard DNA will dissolve hyde glue to the point you can clamp the work and the glue , being reactivated, will set as the DNA evaporates. Have you tried this method? Of course water and heat is much cheaper way to go.

Jerry

Avoid DNA with hide glue. I have heard this before and out of curiosity, it tried it on some butt joints to see if it released any easier. Not one bit better.
After releasing the joints(rub) I reglued with hot hide and found the DNA release joints took longer to set.

All of the tests were with 190 gram glue.

As I do a bunch of repairs on older furnitumre, I find shellac as the topcoat in many cases. Using DNA make no sense as it melts the shellac and it can wick in the joint.

For me it makes no sense at all to use DNA when water does an equal or better job with no risk to joint strength or messing up the existing finish. The hot hide will just pop right off the surface if there is any shellac under the glue so it makes for a neat repair.

All of my testing was with hot hide that I cook up. Occassionally I use liquid hide from Pat Edwards "Olde Brown" glue. He uses urea to slow down the dry time and he dates his glue. Good stuff for keeping around but I would add that I keep mine in the refrigerator when I am not using it. Warm it under hot tap water to thin it down.

hope this helps
Dan