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Steel Repoussť and Granular/Color Spray Techniques: 
An Extension of Sgraffito/Grisaille
by John Killmaster; Professor of Art 
Boise State University Enamels Program 
from Volume 8, Number 3, June 1989

Figure A

     In past years I've utilized cold rolled steel for flat enamel work by fabricating panels using a metal-brake and a spot welder.  
     Tiring of the labor involved, and as a change of pace, I began cutting and hammering free-form shapes to create color relief abstractions.  
     These processes, refined over time as I acquired various hammers and hammering skills, resulted in a form of repoussť which involves working 22 gauge cold rolled steel from both sides.  
     Concurrently, I continued to explore my spray techniques - sgraffito/grisaille1 - to enhance the hammered relief forms utilizing sgraffito-linear and grisaille-tonal effects, along with an additional combined spray technique. . .directional and granular color application.  
     I was satisfied with the monochromatic beauty of sgraffito/ grisaille for much of my work, but I began to enhance the suggestion of warm and cool by using a light liquid enamel spray coat of blue.  
     I found that by using a carefully controlled series of color applications using blue, red and yellow in sequence I could arrive at a full spectrum of watercolor-like veils of color while retaining the expressive characteristics of sgraffito/grisaille.  
     In addition to the color process I began to vary my spray technique, (based on work I had done in painting with the airbrush), by spraying a light mist of white, on fired black, from an imagined light source across the high areas.  This heightened the actual relief and unified the total light and dark illusion of the piece.  
     Finally, I was determined to improve the sgraffito process so I could create line work as sensitive in character as an etching, or pen and ink drawing, while transcending both through the unique enameling qualities that develop through careful firing and additional sgraffito stages.  
     The solution lay in directional/granular spraying, a delicate process worth the time to perfect. 


(1) Metal Working 
Figure 1
     Begin by cutting the shape of the design out of 22 gauge cold-rolled steel.  With a marking pen trace the outline of the design on the metal by using a paper template. (22 gauge steel is substantial and workable for panels from 12" to 30".)  
     Draw in details and cut out steel shape using shears.  (A throatless bench shear, commonly called a beverly shear, is best, but hand or electric shears will suffice.)  
     Next, with a narrow edged metal working hammer, tap lightly along all major interior line details to transfer the image to the back. (Fig. 1 )  
Figure 2     A large hammer is used next to dome out, from the back, the largest areas.  Hammering is accomplished on wooden stumps pine and hardwood; (Fig. 2) pine is best for large areas and hardwood gives resistance for detail work.  
Figure 3     Additional refinements are developed by using smaller hammers on the front to push back recesses and hollows.  By working both sides a variety of forms may be created (Fig 3 and fig. 4).
  Figure 4

(2) Finishing and Welding
Figure 5     Working from the front of the panel, establish a horizontal line, two thirds up from the bottom using a straight edge extending beyond the sides to mark the location of mounting tabs.  Transfer the measurements to the back and mark tab locations.
Figure 6     "L" shaped tabs with a hole drilled in the long end are spot welded in a vertical mode. (Fig. 5)   All sharp corners are filed round to prevent stress and enamel pop-offs. (Fig. 6)

(3) Cleaning and Ground Coating 
     Pickle cold rolled steel in sparex for several hours to clean of rust and scrub with cleanser, rinse, and scrub with baking soda to neutralize acid, then rinse well until a slight rust appears upon drying.  Do not touch the surface!  
     Ground coat is lightly sprayed on the back and thickly sprayed on front and edges.  All spraying is done at 25 lbs. pressure as uniformly as possible, and dried.  Fire at exactly 1500 degrees for 3 minutes.  Impurities are forced out the back using this spray process.

(4) Granular Spray Technique
Figure 7     A black coat is sprayed lightly on the back and thickly on the front and is fired at 1360 degrees Fahrenheit for 3 minutes until glossy (Fig. 7)
     Keeping the glossy black surface oil free, prepare for spraying the white granular coat by setting the air pressure at 10 to 15 PSI. Mix white liquid enamel to consistency somewhere between cream and milk and strain it through a fine tipped automotive (touch-up) spray gun.
     Begin spraying at a 45 degree angle 9or lower) across the panel.  Visualize the "light source" of the design and spray to "bring up" the highlights.  Recesses will not collect as much white spray and remain in "shadow".
     Use a delicate "light touch" when spraying and avoid any wet appearing layering.  Stop before this wet look appears!  Wipe off and begin again if a granular effect does not appear.  Stop and dry each light grainy stage before spraying again.  By three to four passes, the surface should appear covered with a snowy coat of sand-like particles about the size of fine sand grains.  Hold the panel at arms length with a bright light source behind you.  If your spraying is successful a slight shimmer of light can be seen reflecting from the underlying black gloss between each particle.
     Variations in grain size may be developed through air pressure, liquid thickness, direction, and angle spraying variables.

(5) Sgraffito Techniques
Figure 8     Because each particle of dry "liquid" white is a separate entity, a needle-like stylus may be drawn across this grainy surface without dislodging adjacent particles which remain stuck tightly to the black glossy surface. (Fig. 8)
     Fine lines drawn with a needle remain clean when loosened particles are shaken free and lightly blown off.  A multi-pointed stylus may be make and used for cross-hatch effects.  As a variation, use a soft brush to further erode lines to make them darker.  (Save the white grains and recycle them!)

(6) Firing and Additional Spraying
Figure 9     Fire white sprayed panels (Fig. 9) at 1350 or 1355 degrees or at exact (test) softening point for 3 minutes.  Hold temperature to the exact degree! (Fig. 10)
Figure 10     A second white coat (non-granular) is sprayed as a thin mist over the fired panel.  When dry, use a small stiff brush to lift white off the areas to remain gray or black.  Refire as above.  This white enhances highlight areas and builds up whites to survive additional firings.

(7) Sgraffito-Grisaille Techniques

     A second light mist spray, but black this time, is laid on as evenly as possible. (Fig 11)  This coat allows further highlight development by removal of black by brushing and sgraffito.
Figure 11     All fine spray coats must be fired at the exact softening point!  Do not overfire!  Fire for 3 minutes at approximately 1350 degrees Fahrenheit, or as a test run indicates.
     An additional black spray, or two, may be necessary to arrive at full grisaille grays.
     Each firing will soften line work so that the original lines move "back in space" in relationship to the last layering of sgraffito.
     All additional spray coats must be put on as delicate, fine, misted spray to avoid obscuring earlier work.  Firing will give a translucent look to the opaque liquid slush or crackle enamel.  The final effect must be anticipated, since when unfired, sprayed enamel appears more opaque and lighter in value.

(8) Primary Color Application
Figure 12     A light misting of blue crackle enamel is sprayed uniformly, or in a directional manner, and is dried.  As before, sgraffito/grisaille techniques are employed to further develop the enamel.  The blue is brushed off areas which will remain pure red, orange, or yellow, but greens, purple and blue areas must remain blue. (Fig. 12)
Figure 13     Use a stylus, needles, and small stiff brushes to remove blue from intended warm areas and shapes.  For delicate graduations use softer brushes to gradually brush out highlights.  Fire work at 1360 degrees Fahrenheit until glossy, taking care not to overfire.  (Firing time tests should be used for each color.)  The blue fired piece will have a subtle cool cast but will not be apparent until warm color is applied and fired (Fig. 13)
Figure 14     The red coat is applied and developed in the same manner, resulting in purple over blue, pink over white and red brown over black (Fig. 14 & Fig. 15).  Fire until glossy at approximately 1350 to 135 degrees Fahrenheit.
Figure 15     If the blue and red applications were carefully worked out technically and aesthetically, the yellow spray will evoke all the colors; green, orange, earth tones, and bright hues together in complete harmony (Fig. 16).
     Brush out blue, purple, and red areas, and then fire. 

Figure 16

Figure B

  1. Sgraffito/Grisaille Approach to Enameling on Steel, Glass on Metal, Vol. 2, No. 1, Feb. 1983, ppg. 8-11.


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