Metal Leaf Images on Turned Wood
By Steve Sinner

Introduction
Creating patina on metals or metal leaf has been done for centuries. Using some of these methods to produce images on metal leaf has become a fascinating personal pursuit. Controlling the process with any degree of certainty has, so far, proved very difficult. Still, I find the results to be pleasing. Following is an outline of my current methods.

Metal Leaf
Metal leaf can be obtained in many different forms. Precious metals such as palladium, gold and silver are easily available, although relatively expensive. They may be alloyed with each other or with other metals to produce a wide range of color variations. The precious metal leafs are sold in books of 25 leaves each. There are 20 books in a pack of 500 leaves. The size of each leaf is 3 3/8" square.

Also available at much lower costs are copper, aluminum, and several kinds of non-precious alloys. They are generally known as Dutch metal, Schlagmetal, imitation gold leaf, or composition gold. These are packaged the same as precious metal leaf, except that they are 5 ½" square. Thus they are easily distinguished from the precious leafs.

Gold, palladium, and aluminum may be left exposed to the air. Other leafs must be sealed after gilding to prevent tarnishing (oxidation). Since our methods of creating patina are a means of causing oxidation reactions, we can rule out the use of these three metals.

Metal leaf can be obtained at almost any art supply source. Be careful if you wish to purchase genuine precious leaf. Some sources do not make it plain that they are selling composition leaf. The size of the leaf is a good indicator. Here are two reputable suppliers, each offering a great range of leafs and supplies.

Sepp Leaf Products, Inc.
381 Park Avenue South
New York, NY 10016
212-683-2840
800-971-7377
sales@seppleaf.com

Size
Leaf is applied with an adhesive known as size. There are many types available. Basically, size is varnish. The most important consideration when choosing size is the open time required. Open time is the period during which leaf may be successfully applied to the size. Before leaf is applied, the size must come to tack, or dry sufficiently. After application, it must cure, or dry completely. So the three variables are time to tack, open time, and cure time. These characteristics of a given size will also depend on such variables as temperature, humidity, and size film thickness.

I use a finish based on Minwax Helmsman clear gloss spar urethane. It is thinned with an equal amount of Parks mineral spirits. This is applied with a Bounty paper towel to turnings mounted on the lathe, turning at around 30 RPM. Let the lathe run for 15 minutes after application to prevent runs.

For size, I use the same finish that I use to seal & finish the piece, eliminating concern about compatibility problems. When the humidity is low, the open time gets a little short.

I expect the work to last for a very long time, since spar urethane is formulated to remain flexible and will move with the wood.

Chemicals
Patinas are created by applying chemicals to the surface of the leaf after the size has cured. Some chemicals will cause the leaf to temporarily detach from the finish below. See the attached information sheet for details about the chemicals. Note the safety concerns for the chemicals!

Chemicals may be applied in an unlimited number of ways. Variables such as chemical strength, humidity, temperature, light, and time will affect the speed and intensity of the reaction.

Safety
All the usual rules of safety apply. In addition, the chemicals being used present special dangers. Some are toxic, and some are flammable solids. Handle them with due respect, use appropriate safety equipment, and store them carefully. Keep them in tightly closed, lightproof containers, since some are also light sensitive. Assure proper ventilation during use. Dispose of leftover chemicals responsibly. Obtain and read Material Safety Data Sheets for each chemical.

Pre-Finish
Since the masking step of the process involves a water-based product, the wood must have sufficient finish to keep the grain from raising. I apply the finish mixture liberally, trying to soak as much as possible into the wood. The excess is wiped off, and the piece is allowed to dry overnight. It is lightly sanded with 600 or 800 grit, and the process is repeated if the wood shows any dull spots. Once no dull areas can be seen, one or two more coats toweled on and not wiped are usually sufficient.

Masking
Some means of masking must be used to determine the areas to be covered with leaf. Masking tape could be used, but can be troublesome on the compound curves of a turning. A liquid masking material is available that works well. It may be purchased from most art supply stores in small quantities at high cost. Automotive paint suppliers also carry it, at less cost than art supply stores. But the least expensive source I've found is sign supply companies. The brand I use is Spraylat Sign Strip. A gallon will cost around thirty dollars. It is made by:

Layout
Using a Rapidograph technical pen to do the layout lines works well. I prefer a very fine line (.013mm) for accuracy. Keep the turning on the lathe and make or buy a table for your tool rest. Adjust table height until the pen point is exactly even with the centerline of the lathe. Then you may draw lines from top to bottom of the piece, using the lathe's indexing abilities if desired. Circumferential lines may be drawn by using a guide clamped to the table. Lightly rest the pen against the turning and rotate it away from you slowly, by hand. Diagonal lines may be drawn by using a .008 feeler gage as a straightedge.

Shellac
Once your pattern has been laid out, do not cut any of the lines before spraying on a coat of shellac. If there is no shellac, the size will not dry on any masked area for a very long time. This will cause serious problems when applying the leaf.

Cutting
Cutting the patterns may be done using the table, feeler gage, and guide in much the same manner as laying out the lines. A wooden handled chip carving knife with flat-sided handles will work fine on the table and guide. Against the feeler gage, you may use an Exacto knife. It does not take much effort to cut through the masking material. Avoid cutting into the wood, as cut marks may show up later.

Remove the parts of the pattern you wish to have covered with leaf. Do this carefully to avoid scratching the surface.

Applying Size
Apply the finish mix in the same way as you would put a coat of finish on the piece. Be sure to get an even coat, and do not try to make it a heavy one.

Determining Snap Tack
With this mix, snap tack will occur in about thirty-to-ninety minutes. Touch a clean knuckle gently to the size on an area that will receive leaf, and when you pull away, you will hear and feel a little snap. If your skin does not stick, the size may be too wet. If so, there will probably be some finish on your knuckle. If too dry, the skin will come away clean.

Applying leaf to a too wet surface will cause the size to seep through the leaf. If it's too dry, the leaf will not adhere.

Simply press the leaf against the size and pull the paper away. Little cracks or spots without leaf may appear. They're called holidays, and they may be covered by pressing another piece of leaf over them.

Pounding Leaf
Once the entire piece is covered with leaf, it is necessary to "pound" the leaf. This is done with a soft brush. The intent is to force the leaf into every corner of the pattern, and be certain that it is tightly attached. Just keep tapping with the brush until all the leaf has been pounded. You will find it easy to see the difference between the pounded and unpounded parts.

Positive and Negative Images
Once the leaf has dried overnight, you may begin the patina process. By now you should have decided if you wish to use a positive or a negative image.

Positive images can be cut from paper. Plain copy paper works, as will tissue paper. The tissue will probably not work if you wish to reuse it. Copy paper images may be used many times if handled carefully.

Negative images can be created on a copy machine or laser printer. Use the darkest settings and don't forget to reverse the image.

Applying Chemicals for Patina
When creating positive images, a hypodermic syringe is used to place the chemical on the paper.

If the image is to be negative, use Xylol to transfer the image to the metal, then spray the chemical on with an Aztek airbrush.

Once the chemical has reached the level of reaction you desire, stop the reaction by gently laying a wet paper towel against the leaf. Do not move or slide it, as the leaf is very fragile at this point. Lift it off, and dry the leaf in a similar manner with a dry towel. For negative images, use a Q-tip and acetone or Xylol to remove the toner. This must be done with great care, or the leaf will be scratched or removed.

Apply a light coat of finish and allow the piece to dry overnight before removing the rest of the mask.

Removing the Remaining Mask
This is done in much the same way as the first part was removed, but be careful to avoid tearing off any of the leaf. Generally, pulling the mask off along and parallel to the edge of the leaf will give a clean edge. Watch for tiny pieces of mask that may be left behind, as they will cause problems later.

Adding Details
At this point, it is a good idea to apply one more coat of finish before adding details with paint or ink. Then, if a mistake is made, it can easily be corrected without damaging the leaf.

Finish Coats
Once all the details are complete, final finishing may begin. After a couple of coats, let the piece dry overnight, then wet sand with 1500 grit and mineral spirits for lubricant. The intent is just to remove the ridges around the edges of the leaf and no more. You may dry sand with 800 grit 3M abrasive. Be careful. Go a little too far with this process and the piece will be ruined.

Proceed with additional coats of finish until you are satisfied. As many as three a day may be added. Wet sanding once each day will help to level the finish, but be careful!!!

Abrasives
Finding and purchasing top quality abrasives can be difficult. I have tried abrasives from Sweden, Germany, and Japan as well as the U.S. The best I've found to date are made by the 3M Company right here in the United States. The problem is that they are generally sold in very large quantities to large commercial users. They are expensive, and are therefore unlikely to be sold in retail stores.

My favorite system is hook and loop, and I use mostly 2" and 3" disks. Grits from 150 to 1500 are used. The types of 3M disks that I feel give the fastest, highest quality sanding are the 366L Hookit Imperial Finishing Film and the 260L Hookit Finishing Film. The 366L is micron graded, 3M's term for an extremely high quality product that has none of those occasional stray grit particles that ruin your sanding job by leaving odd scratches. The film backings on both of these products are very tough. There is no need to have fluted edges on the disks, since the film is quite flexible and will not dig in.

For the equivalent of P150 to P400 grit, the 366L is available in 6" disks. From P600 to P1500, the 260L is available in 3" disks. I use cutters made from hole saws to cut two 3" disks and two 2" disks from each 6" one with an arbor press.

These abrasives can be ordered from R. S. Hughes Company, which has more than thirty locations in the U. S. and Mexico. Their toll free number is
877-744-8443, and their web site is www.rshughes.com. At the time of my last order, the 3" disks were $0.39 each, and the 6" disks were $0.60 to $0.80 each.

Here is a handy abrasive grit comparison chart to be used as a general guide:

Bryant Laboratory
1101 5th Street
Berkeley, CA 94710
415-526-3141

City Chemical Corp.
132 West 22nd Street
New York, NT 10011
800-248-2436

Ask for an MSDS for each chemical to be included with your order, and read it before you use the chemical.

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