I have talked on the phone with Tracy, but for the edification of other listers, I will summarize my comments. The problem is a wooden molding on a table that has been traumatically broken into a number of pieces, some very small. An old glue joint is not involved.
The concerns from a conservation perspective are a) the pieces may have distorted and may not fit tightly back together; b) a finish is present on the wood, and any solvent in the adhesive must not harm/remove the finish; c) it must be done right the first time, because it is exceedingly hard to separate broken wood pieces after the glue has set even if a reversible glue is used.
a) Dry fit all the pieces together. If there is distortion, figure out how to correct it, and keep dry fitting until everything goes together correctly. Determine if some sort of clamping system is needed, as often there is tension in traumatic injury to wood. The wood cells can actually become stretched and require pressure to go back in place.
b) The solvent in the glue itself is not the only concern. After the glue has been applied and the pieces fitted together, there will be glue "squeeze-out" residue that needs to be removed from the surfaces. No glue squeeze-out means that not enough glue was used and the joints may be starved of glue and weak. Most B-72 is supplied in acetone. This will remove most finishes, so is not a suitable glue for this situation. It also sets up far too quickly to allow all the pieces to go back together before it has dried. It is possible to dissolve B-72 yourself in toluene. This would have greater working time and most finishes are not affected by toluene, but it is not the best health-wise for the user, so would not be recommended in this situation. Araldite and other epoxies are not reversible and for a repair such as this are inappropriate. Additionally, they are too thick and will prevent the pieces from correctly aligning. Titebond is not as reversible as other alternatives and also may create too thick a glue line. I would recommend fish glue, a form of hide glue, which I get from Lee Valley Tools. It has an open working time of 20-30 minutes depending upon the temperature, which should be adequate. Other types of liquid hide glue are made using formaldehyde to keep the glue liquid at room temperature and I recommend against these. Hide glue in its natural state is a gel at room temperature and must be heated to be applied. It is not appropriate for this situation since it will cool to a gel far too fast to get all the pieces back together.
c) Put the fish glue on all the pieces and fit them together as a unit. Apply clamping as necessary. Be sure everything is properly aligned. If not, disassemble everything, wipe off the glue, and start over. Do not allow it to dry out of alignment. Wipe off the excess squeeze-out with a water-dampened cloth. Let the glue set overnight, remove the clamping system if any, and clean up any remaining glue on the surfaces with a water-dampened cloth. Do not try to glue one piece at a time, or you may end up with lockout - later pieces can not be fit in place.
Marc
American Conservation Consortium, Ltd.
4 Rockville Road
Broad Brook, CT 06016
www.conservator.com
860-386-6058
Marc A. Williams, President
MS in Art Conservation, Winterthur Museum Program
Former Chief Wooden Objects Conservator, Smithsonian Institution
Fellow, American Institute for Conservation (AIC)
From: Tracy Brindle
Sent: Wednesday, August 12, 2015 8:51 AM
To: [log in to unmask]
Subject: Re: [MUSEUM-L] Repair of wooden objects
Thank you for the responses. I have used acryloid in making minor repairs to glass and ceramic, but was not sure about its effects on wood.
-Tracy
=========================================================
Important Subscriber Information:
The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes).
If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).
=========================================================
Important Subscriber Information:
The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes).
If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).