There are endless possibilities when it comes to creating a design on a piece of glass, but it's possible to record the steps taken for a particular project. There are some gaps in my knowledge, but here is how the project came together from my perspective:
Design:
Larry created the design, so that was already done when we got there. I know other people helped create the prototype and get the meet ready, but I'm not sure who did what.
Two silkscreens were made - one for the gold areas, and one for the black areas. Each screen had an identical set of registration marks. Before our arrival, each piece of glass was aligned to one of the screens, and printed with a set of registration marks. The registration marks made it possible line up each stage of the project perfectly on the glass
Each person received a vinyl mask for chipping and etching - registration marks were in the vinyl as well
Etching:
The acid paste was made from hydroflouric acid, with mica chips added. Food coloring in the acid paste indicates how big the mica chips are - 4 different sizes. Each size gives a finer or courser texture in relation to the others. The coloring also makes the acid easy to see, in the case of accidental contact with skin.
We applied the vinyl mask to the back of the glass using the registration marks. First we completely cut out the registration marks on the vinyl and backing paper. When the registration marks on the glass were visible through the holes in the vinyl mask, the vinyl was taped in place, hinged, and applied.
After the mask was applied, we covered the front and sides of the glass to protect it from sandblasting and acid fumes. We used application tape on the front, and then patched up the smaller areas with tape. Plastic tape works better than masking tape because it doesn't absorb any of the acid. We removed the vinyl from the parts of the design that were to be be acid etched, and taped over the area that would later be chipped.
Disposable surgical gloves are worn under heavier rubber gloves as an added protection. Hydroflouric acid can be very dangerous, as it has an affinity for calcuim...in bones. We were very careful to avoid any contact with the acid.
A vinyl squeegee cut in half, across the ridges, makes two mini squeegees. These are used to scoop out the acid paste - like serving salad. The acid paste is applied to the exposed glass in a fairly heavy layer, and allowed to remain for 30 minutes.
Once the etching was complete, we scooped the acid paste back into the container - it can be re-used. We rinsed off any acid residue with water - sprayers were used first, and later cups of water were poured over the glass
Sandblasting:
Sandblasted glass gives a better surface for glue chipping than smooth glass. We removed the vinyl from the parts of the design that needed chipping, and taped over the etched areas. We put the glass into the blast cabinet, and blasted until the shine was completely removed from the chipping area. I can't remember specs on the sandblasting equipment. It was powerful enough to carve the glass, but I'm wondering if something like an air eraser would also be sufficient to create a glue chipping surface.
Applying the glue:
In this case we didn't use the asphaltum method so the vinyl mask remained in place when applying the glue. The glue was heated in a special glue pot, but I'm told that it can be heated in the microwave. To contain the glue, a rectangle-shaped dam was made from pieces of stiff cardboard and tape. A wooden block was used as a template to mark where the dam would be put - this kept each dam the same size.
The surface area inside the dam was used to calculate how much glue to pour on - I can't remember the ratio. With the surface level, the glue was measured in a pyrex cup and poured into the dam. The glue layer ended up around an 1/8" thick, or perhaps slightly less.
We waited until the glue had set up to the point where a cut in the glue with an exacto wouldn't "heal". We traced around the edges of the letters with the exacto, to separate the letters. Once the letters were separated, we removed the vinyl mask, and the excess glue came off with it - all masking was removed from the glass. What remained was the glue in letter shapes on the clear glass
Chipping:
The glass was put into a chipping booth and we waited for the glue to dry. At first there was no heat in the booth, and no chipping occured the first day - Friday. The next day heat and fans were going, and it still took quite a few hours to chip. A drier climate would have made for faster chipping, and the heat and fans probably wouldn't have been necessary.
My piece was at the point where it was mostly chipped, but there were still certain places that hadn't chipped. I was sitting around waiting for hours, and then Frank Maesen showed me how to "help" the chipping by tapping or prying on the dried glue with the tip of an exacto knife. Using that method I was able to get all but the smallest bits of glue off. After the chipping I put the glass in the sun and covered it with wet paper towels to soften up any remnants of glue. The glass was then rinsed off with lots of water, and paper towels were used to remove any traces of glue
Cleaning:
The glass needs to be super clean for gilding so I first cleaned it with a slurry of whiting and ammonia. I'm not sure what strength the ammonia was, but it smelled pretty strong. A small scoop of whiting was dropped into a dixie cup, and ammonia was added to fill the cup to be about 1/3 full. The whiting and ammonia was stirred with a popcicle stick until it was completely mixed.
I pulled a wad of loose cotton from a bat of cotton that was nearby. Then I poured part of the mixture onto the glass, and went over the glass with the cotton in swirling patterns. I did this on both sides of the glass several times. I was wearing surgical gloves during the cleaning to avoid contamination from my hands. after each cleaning I would spray off the glass with a hose.
later I was told to try a different method for the final cleaning on the back side. I can't remember but I'll assume I was using a paper towel. I got the paper towel wet and rubbed the cake of Bon Ami until a good amount was on the paper towel. I started cleaning the glass with swirl patterns, covering the entire surface, and reversing the swirl direction periodically. Then I would let the Bon Ami residue dry completely, and I'd wipe it off with dry cotton in swirling motions, or paper towel - can't remember. I repeated this at least 3 times on the back side of the glass
Gilding:
Larry uses cement mixing tubs to catch the excess water and chemicals that run off the glass during the gilding process. A similar setup is used for the acid etching. There is a wooden "H" made of 2x6 lumber in the bottom of the tub. A plastic diffuser grid for lighting is placed on top of the "H" and this becomes the working surface.
The glass is placed on the grid, with the back side facing up. The gilding instructions are found on angelgilding.com, but I'll do a very basic overview.
A layer of distilled water is sprayed onto the glass to keep dust from collecting on the surface. The distilled water is poured off when the tin solution is ready. The gold can't stick to the glass by itself, so a tin solution is put down first. The tin sticks to the glass, and the gold sticks to the tin. The tin solution stays on for a specific time, and then gets poured off. Distilled water is then used to rinse off the remaining tin solution. The gold solution is mixed up and poured onto the surface of the glass. This is allowed to stand for around 20 minutes if I remember correctly - perhaps longer. The gold will start to attach to the glass, and the glass becomes reflective
Once the gold is finished, the solution is poured off, and the glass is rinsed with distilled water. A final solution of silver is applied, and this adds to the luster of the gold. The silver is poured off and the glass is rinsed again with distilled water.
The glass needs to dry, so it is placed against the wall, in a vertical position - this keeps the water from pooling on the glass. Once the glass is completely dry, it is ready for the first screen print. At this point the entire surface of the glass is a dazzling gold mirror
First screen print:
The first screen print will determine which parts of the design will remain in gold. A screen print is probably more accurate, but I don't see why vinyl mask couldn't be used if screen printing weren't an option. "Backup Black" is used for the screen ink - it likes to dry quickly, so speed is important when doing multiple prints. We had problems with some breeze coming in and drying out the screen. The first screen print is applied to the glass, and it's dry in a very short time.
Clean off the excess gold:
The backup black protects the areas that will remain gold. Once the screen print is dry, the excess gold and silver gets removed with silver strip. Wear gloves in this process. Little self-adhesive foam squares are stuck to the front surface of the glass - this allows the glass to be placed flat without getting scratched.
With the glass flat, silver strip is sprayed onto the surface - this is done by treating a limited area of the glass at one time. Cotton is used to remove the excess gold and silver. The silver comes off easily with silver strip, but the gold actually comes off with the pressure of rubbing. The cotton loads up quickly, and you need to keep turning it over and folding it to assure you are always using a clean piece of cotton. Once all the excess gold is gone, the design shows up in shimmering gold on the front - no black is seen from the front yet.
Note that on the chipped letters, the silkscreen is designed to print wider than the chip. This creates a smooth gold outline around the chipping
This is called the "bright line"
Second screen print:
The second screen print establishes the black outlines and drop shadows around the gold
Finishing:
This is where the possibilities become endless - each person seemed to go in a radically different direction. I used abalone chips in one area. To do this I put down a layer of Fibroseal, sprinkled on the chips, and let dry. Then I put a layer of Fibroseal over that entire accented area. I'm not sure how the larger pieces of abalone were applied - possibly the same way as the small chips. Most people were using 1-shot for coloring the back, and lots of blends and faux finishes were used. The finishing is the part that requires the most skill in my opinion, because it isn't a mechanical process. Each area can have a different treatment, and it's all up to the imagination of the artist.
Attaching the photo to the circle:
I didn't get to see how this was done, so I'm not sure of the best method. I've read about how to do it, but I'd be interested in knowing how Larry would do it.
Design concept:
When I design my own project, here are the guidelines I will be following:
Denver Chapter of the Letterheads