REGALREZ IN FURNITURE CONSERVATION
Assuming that what was found to be safe on paintings would also be safe on furniture, I applied Regalrez 1094 on a privately owned bed in the Biedermeier style likely from southern Germany, dating around 1840. The old finish on the bed was somewhat opaque and had yellowed, thus obscuring the color, depth, and grain of the wood. A 10% (w/w) solution of Regalrez 1094 was used in white spirit, adding 2% Kraton G1650 and 2% Tinuvin 292 to the weight of the resin. The solution was applied with a cotton swab, and it produced a smooth finish with a pleasing depth. The undesirable effects of the yellowing and opaqueness were significantly reduced by the saturating qualities of the resin, and the varnish largely regained its transparency. The finish felt dry to the touch, but even two years after application it became tacky after a hand was placed on the surface for a short period of time.
2.1 POSSIBLE CAUSES OF TACKINESS
This tackiness may have many causes, including:
- the old finish on the bed
- the affinity of Regalrez 1094 with the nonpolar solvent, causing a longer solvent retention
- the nature of the components: Regalrez 1094, Kraton G1650, or Tinuvin 292.
These are the possible causes tested here.
2.2 TEST METHODS
Several different mixtures were made for the test (tables 2 and 3) following the instructions of Whitten (1995a) making a 10% (w/w) solution adding 2% Kraton G1650 and 2% Tinuvin 292 to the weight of the resin. All varnishes mentioned in this article were made using these concentrations, unless otherwise stated. The mixtures were brushed on thin glass sheets. This inert substrate was used so that any tack could be caused only by the mixture applied on top. In addition, Regalrez without any solvent was melted, and a film was poured out over glass. Each film was left to dry for three months at room temperature, after which time a hand was pressed against it for 10 seconds to detect tackiness. This test was repeated after another three months. The amount of tack was not quantified because if a finish gets tacky upon handling, it is not appropriate as a top finish on furniture, regardless of the degree of tack.
The hand temperature of 15 people was measured by letting them hold the bulb of a thermometer until the temperature stabilized. The room temperature at the time was 20-22°C. The range of hand temperatures was 31-35oC, the average being 32-33°C. This average may differ when testing a larger group or testing at another room temperature, but it gives an indication of the temperature that can develop at the interface between hand and object during handling.
The Six Solvents Used in the Tests