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Past Articles from Glass on Metal

A Revolutionary New Blockout Technique 
for Etching Metal
by Katharine Wood with Paul Silverman
Photo Credits:  Paul Silverman
from Volume 15, Number 3, August 1996

Photo 1 - Enchanted Forest by Katharine Wood

     One of the great satisfactions of etching is that whatever you can draw, you can etch.  However, if you have an elaborate design, the application of the resist can take many hours.  But now, the etching process will be radically changed by a technique developed by Paul Silverman, which I have further refined for enameling.

     A photographer by profession, Paul began experimenting with etching in an attempt to simplify the photo-etching process.  Realizing that printed circuits had to be etched with total accuracy, he utilized this technology and has come up with an incredible new method of blockout for champleve and basse taille enameling.

     In recent years, much has been made of Xeroxed images and their direct transfer to metal.  This method was initially intriguing and still performs well for a light surface etch.  However, its limitations become distinctly obvious when a deeper etch is required.  Small lines do not hold up; larger areas develop pinholes.  With this new technique, the finest lines can be quickly applied and then etched with complete accuracy for many hours, resulting in a clean, deep etch.  Paul has generously supplied all his notes for this article.  As an artist and teacher of enamel, I have tested his findings and expanded on them with my own work and in the classroom.

Figure 1     The first step is the same age-old step that precedes all enameling - clean the metal!  It is especially important with this technique to clean very well.  Unfortunately, there will always be some who will not succeed simply because they have not taken the time to clean well enough so that the water 'sheets' on the metal.  Cleaning consists of scrubbing with Scotch-Brite or similar abrasive sponge and cleanser (with chlorine).  Rinse well, and finish off by cleaning the metal with alcohol.  Hold the piece carefully by the edges.  Wear surgical rubber gloves (available in any hardware store) to hold the piece, so that no finger grease is transferred accidentally onto the edges - and, don't forget to clean near the edges of the metal.  If there is a 'lip' or 'burr' at the edge of the metal shape, which may occur from machine cutting, it must be filed off before cleaning.  This is very important, as the metal must be completely flat, with no warpage or areas even minutely raised.  The reason for this will be obvious later.  However, leave the burrs on the back of the piece; this will stop the metal from sliding during transferal.

     In the meantime, you should have a sheet of PnP blue paper already Xeroxed with the images you want to transfer.  This PnP blue paper is a fairly new invention used to transfer printed circuitry to metal.  It is available from Thompson Enamel.  It comes with full instructions on how to use, but a little clarification is in order.

     First of all, select the image you want to etch.  It can be your own design or it can be a copyright-free design from, for example, a Dover design book.  The important thing is that the image must be high contrast, i.e. black and white.

Figure 2     In theory, no half-tones or shading - although one might consider experimenting at some point and seeing what happens.  Also, no color images.  Remember, in etching you are simply dealing with positive (the raised unetched copper) and negative (the etched-away areas).  Therefore, you need a pure black and white image - although it can be as detailed as you like.  Note that this technique works best if the surrounding area of the image is black; the more area transferred, the better the adhesion.

     Next, run your image through a Xerox machine onto the PnP blue paper (onto the 'dull' side).  Be warned - some copiers cannot handle this thick, acetate-like paper.  Be especially wary of older machines with rollers inside; they can jam.  Use the newer direct feed machines that do not overheat.  The key here is to experiment.  I have had success on a number of machines.  Be sure  your Xeroxed image is dark; you might want to press 'darker' on the machine.  Just be sure there are no smudges on the printed image.  Also, it saves time and money to cut and paste several designs onto one sheet of paper (black construction paper works best).  Xerox the whole collection at one time onto the PnP blue, thereby filling up the sheet.  The different designs subsequently can be cut out and used when needed, and there is little waste.  One warning:  everything comes out reversed when transferring, so take this into account, especially with lettering.

     So, now you have a very clean, flat piece of metal and a sheet of PnP blue paper filled with designs.  Choose the image you want to transfer.  To center or register image, outline your metal shape on the PnP blue artwork and cut out neatly.  Cut the transfer slightly smaller than the metal (otherwise the image might lift off the metal), but leave one edge flush with metal edge.  Make pin holes in the PnP transfer sheet to line up with punch marks in the metal.  Next, still wearing your surgical gloves, place the metal onto a piece of wood.  You can tape it on from the back so it doesn't move around during the next step.  Get out the iron.  Yes, the one used for clothes!  Set the temperature on 'high' and wait until it is heated up.  Give the metal one last swipe with alcohol, as copper oxidizes quickly.  The dull side of the PnP paper should be face down making contact with the metal.  Start ironing outwards at the edges of the paper first, rotating the piece on the wood until the edges are tacked down.  Continue over the rest of the piece.  Keep the iron constantly moving in a circular motion.  Watch for wrinkling and bubbling of the PnP paper and iron down promptly, turning down the temperature setting a little.  Do this for five minutes; larger pieces may take longer.  Again, experiment!  Ironing should be smooth; light pressure is all that is needed.  The design should start showing black through the PnP sheet.  When this occurs, continue until design shows completely in black, and then stop ironing.  Let the piece cool totally, it will be very hot.  Then, starting at an edge, peel the PnP sheet slowly and carefully off the metal.  The iron can be cleaned, when cool, with a swipe of acetone.

Figure 3     What you should now have is a completely accurate and (almost) perfectly transferred image in black (this acts as a resist) on your copper.  And it only took about five or ten minutes!  I say 'almost perfectly transferred image' because sometimes there will be areas that need a little touching up.  Sometimes a fine line is broken in one spot, or a large area needs extra protection.  In these cases, simply take traditional resist (asphaltum, for example) and touch up or cover those areas.

     Can you over or under iron?  Yes, to both of these, but there are simple remedies.  If you have under ironed (too little time or too low temperature), the transferred image will show up blue instead of black.  If it is really under heated, the image will not transfer at all.  If you do not remove the PnP paper, but simply lift a corner and peek, you can lay it down again without moving the image (keeping perfect registration) and keep ironing till the image shows black.  Actually, I have etched some pieces with the 'underdone' blue resist, and it still holds up pretty well.

     If you over iron (too hot or too long), you will have areas of blue showing within small sections of the transferred black design.  In other words, fine lines will 'block up'.  In this case, simply take a scribe or pin and gently scratch off these parts.

     Finally, cover the back of your piece with contact paper.  Trim the edges.  Graphing tape (available at art supply stores) in different widths is good for borders - both for the original drawing and the metal piece.  Edges as well as borders also can be covered with electrical tape folded over the back.  Or you can paint by hand a curved or irregular border with resist (don't forget resist on the edges).

     You are now ready to etch!  I use ferric chloride on copper; it can be used on nickel silver and brass, but the ironing takes somewhat longer, and these metals are not good for enameling.  Nitric acid is no good for this method.  If you want a design  in fine or sterling silver, you must either have the copper original cast (sterling) or roller-print it onto the silver (fine), using very thin copper as your master.

Terra Incognita II by Katharine Wood

     As always, the piece must be placed face down to etch in the ferric chloride.  I put it on top of a thicker version of Scotch-Brite, saturated with mordant, in the solution.  If you have a regular, thick enough border, you can use self-stick plastic furniture protectors ('cushion feet') for support.  From this point, all the regular rules for etching apply (see my article in Glass on Metal, Oct. 1990).  After etching, enamel can be applied.

     The only limitation for this technique is that you cannot 'double etch' with it, since the receiving metal must be flat.  If you want a double, or multiple, etch, this must be done in the traditional way, with hand and brush and regular resist.  A whole sheet of metal can be patterned and then cut out into jewelry shapes or cut and sculpted.  It does not even have to be enameled, but can be used for many jewelry applications with a textural background.

     Enjoy this wonderful new technique; it will open a world of possibilities to the imaginative enamelist and metalsmith. 

 

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