The Rot Doctor


Subject: Preservation of Historic Live Oak Tree Cookies
Date: Wed, 22 Jan 2003

Dear Rot Doctor,
I need help with a project that involves trying to preserve several (more than 50) large (maybe 6ft. or 7ft. in diameter) tree cookies cut from a very old dead live oak tree. The tree has been dead for over 5 yrs. now, still standing it will soon be cut into tree cookies. I am science teacher and my plan is to distribute these tree cookies to each of the schools in the county where I live. I would like to give the schools some idea about how to preserve these cookies so that they will not split. Then the teachers can use them to teach science lessons as well as develop a historical time line from the annual rings. I also plan to put the largest of the cookies on display in the County Courthouse with a historical timeline of the County.

I need a simple, low cost way to preserve these tree cookies that will still allow the rings to show up. If you have any ideas on how to get the rings to show up better, I would like to hear that as well. Can you help?

Margaret S.

I would soak them in CPES. This absorbs into the wood and fills any voids with epoxy. This will keep them from splitting. It will also darken the grain slightly, making the rings show up better. Each cookie will probably absorb somewhere between 1 pint and 1 quart of CPES.

CPES, like any epoxy, will not stand up to sunlight well over time. Exposed to sunlight, the epoxy will yellow and break down. If you preserve the cookies with CPES and it does yellow over time, it would be fine to sand the surface and either leave it natural, or stain it to show the rings. Over all, I think that CPES is the best product to use, and that you will be quite happy with the results.

I would lay each cookie on 2-3 layers of visquine, the plastic painter's drop cloth available at home stores, gather the layers up to form a close container around the wood, and pour in CPES until it just covered the wood. I would allow it to soak, topping off as needed, for 1/2 hour to 3/4 hour, then syphon off any excess and allow the CPES to cure. If you don't mind a little shininess to the wood, this is enough, If you want a more natural surface finish, I would wipe down the surface with lacquer thinner. All this will be somewhat smelly, so organic fumes respirators and plenty of fresh air is called for. As well as vinyl gloves for handling the wood and CPES.

If you have further question, please let me know.