Updated: Jan 2
While working on this small export lacquer box earlier this year, one of the major questions was what to do about the coating in the future. The urushi on the surface had been severely photodegraded (damaged by UV light). This urushi lacquer surface, with it’s maki-e decoration (springled gold) is essential to this piece, however, the lacquer itself had become unstable.
Shayne Rivers has written previously about the ethics involving this decision. Conservators have gone on record using wax as a coating over top of the degraded lacquer, as well as modern synthetic varnishes such as Paraloid B72. Shayne has advocated the traditional Japanese conservation approach of repair through Urushi-gatame, an application of new urushi into the surface to fill the microcracks that have formed from degradation.
In order to make that decision on this object, I reviewed the criteria.
Client/Ownership: The object was privately owned, and likely to go back into their home.
Handling: The client expected to be able to handle the object with their hands, to open it and close it, and to show it to others.
Usage: The client might want to use it to store things inside of, they might leave it out on a table or shelf.
Reversibility: If possible, it would be good to remove the work I had done to return the piece to where it was before I started.
After advising the client that it is best to leave the box somewhere outside of direct sunlight in order to ensure it lasts, it was still essential that they be able to touch it with their hands without damaging it.
I considered an urushi-gatame repair, but given resources and support at the time, it was decided that I would explore a modern synthetic option. The question was which one.
Larapol and Paraloid
After some suggestion from Shayne Rivers herself, I looked into the use of Larapol A81. I had attempted Paraloid B67 with decent results, but B67 is currently raising concerns of cross linking over time, and an inability to be removed later on. I was able to carefully remove the B67, and began exploring sprayed coatings of Larapol A81.
Larapol A81 is a low molecular weight resin, which can be sprayed in higher concentrations than Paraloid B67 or B72. I combined it with Shellsol A100 and sprayed several test coatings. The results were visually appealing, providing good saturation and return of gloss, but even after a couple weeks of drying, I would still leave fingerprints in the surface when handling anything I tested.
Larapol A101 had similar results with my equipment and methods, so I started looking at alternatives. I found a paper written in 2000 by J.M. Arslanaglu on Larapol A81/Paraloid B72 blends. It was with the results of this paper in mind that I started my own tests.
In the end, after multiple combinations, I settled on a 1:1 ratio of Larapol A101 and Paraloid B72 disolved 22% w/v in Shellsol A100. Three coats of this varnish were carefully sprayed over the box with some success.
Burnishing the Varnish
That said, after a few weeks with this varnish on, I was still dissatisfied with the result. The consistency after spraying wasn’t as satisfactory as I would like, and the feel when handling was not entirely solid. If forced, I could still leave fingerprints in the surface.
It was at this point that I decided to attempt a burnishing technique that I had not read about previously. I didn’t want to abrade the surface in any way, for risk of damaging the Maki-e decoration beneath. Abrasion even with the finest of micromesh would still leave scratches and not provide the gloss levels my client desired.
Instead, I turned to my understanding over thermoplastic burnishing techniques used in traditional shellac and wax polishes. I warmed a soft cloth I had previously washed a few times in warm water. Wadding the warm cloth up in my hand, I polished the surface with a decent amount of pressure. Certain I had properly consolidated the layers before, I was able to press quite firmly on the surface.
This burnishing process warmed the thermoplastic coating, and allowed me to compress the polymers into a denser and smoother state. This increased resistance to handling and increased gloss.
The results were satisfactory, and the objects were able to be returned to be used again.