JARS v50n1 - How To Make Engraved Garden Labels On Photo-Sensitive Aluminum

How To Make Engraved Garden Labels On Photo-Sensitive Aluminum
Dorothy M. Dunstan
Portland, Oregon

At one of our workshops during the 1994 ARS Annual Convention in Asheville, N.C., I mentioned that photo-etching is an alternate, less expensive method of making permanent labels for the larger public or private garden. It was requested that I write a descriptive article on this method for the Journal.

The Hoyt Arboretum in Portland purchased - or made up - the equipment involved in doing this photo-etching process and has made the facility available to Portland Park Bureau Gardens for label making. We, at Crystal Springs Rhododendron Garden, have been making plant labels at the Hoyt Arboretum for the past five or more years, and they have held up very well. The labels are used on both trees and rhododendrons in the garden.
The 12-inch by 20-inch (several other sizes are available) special anodized photo-sensitive aluminum sheets are purchased from Fotofoil Division/Miller Dial Corporation*, a California firm, at approximately $20 per sheet. They come in a selection of colors and gauges with gloss or matte finish. We use .032 gauge black (for rhododendrons) and green (for trees). The preparation of the written material for the signs is done to maximize the use of the aluminum sheet. The sheet must be cut to a size to accommodate the tanks.
It is necessary to make good, sharp transparencies of the material to be photo-etched. The transparency is then placed on top of the aluminum in an enclosed pressure frame with a glass top. Firm pressure keeps the transparency from drifting about during exposure. The glass top permits the ultraviolet light rays to penetrate to the photo-sensitized aluminum. It is then exposed under ultraviolet light for a few (3) minutes. There are four 2-foot fluorescent black light tubes, marked F20T12/B2 20 watts, in a separate box above that fit into the top of the pressure box above the glass. It also helps to have a couple of timers handy.

Nearby there are two tanks for developing and etching. The etch tank is heated to a comfortable 90°F-95°F by a heating cable wrapped around the tank. A fan must be used to ventilate the room during the process, and eye hazard caution is necessary because of the nature of caustic soda. The tank should be adjacent to a sink with a spray nozzle on the faucet. The next step is to place the exposed aluminum on an expanded metal clipboard and then place in the tank of developer for a few minutes. Spray-wash thoroughly after removing from the tank and then place in the tank of caustic soda for another time period or until the etching is completed so that it shows the printing clearly and sharply. Both cold and hot water are used in spraying. Following this, another spray washing is necessary. Also, the aluminum must be wiped off with a rag or paper towel during the rinsing to remove colored material from the backside of the sheet. If the letters are not precise enough the sign may be returned to the last tank and the process repeated. This all should result in clear readable signs. The tanks should be kept covered when not in use to prevent evaporation or material and fume dispersal. The chemicals in the tanks can be added to but need not be replaced. The next step is to shear the metal to your required size and to drill or punch holes in it for attachment.

At Crystal Springs we attach the sign by screws or pop rivets to a sheared metal piece of the same size that has been welded to -inch by 1-inch bent steel bar. It is then partially buried in concrete or backfilled with dirt. Another method of attachment is to shear the material into strips of 6-inch long by -inch wide, punch holes near each end, bend over a piece of plastic pipe and pop rivet around a branch. This is a good solution that is not too conspicuous. Injudicious pruning of the attached branch or excessive growth causing binding are reasons to be careful if using this method of signage.

* Photofoil Division/Miller Dial Corp. 4400 N. Temple City Blvd. El Monte, CA 91734.

Dorothy Dunstan is a member of the Portland Chapter.