GLASS CHIPPING

The art of decorative glass chipping
     with hide glue consists of the following steps:

• Preparation of the glass surface.

• Pouring the warm animal glue solution
     upon the glass surface.

• Gelation and preliminary air drying of the glue film.

• Oven drying of glue film and subsequent chipping
     of glass surface.

• Finishing of the chipped glass surface.

Getting Started:
(1) Lightly sandblast or etch the area of flat glass to be   chipped (pre-etched glass is also available).

(1a) Tape the outside edges of the sandblasted area with masking tape to create a dam or containment for the liquid glue.

(2) Measure area of glass to be chipped and convert to square inches to square feet.

(3) Prepare a one to two part glue / water solution using the Glass Chipping Glue (GCG) by soaking the one part, by weight, dry glue in two parts, by weight, clean, cold water for one hour. Then melt in jacketed containers at 135 - 145°F. Let stand at this temperature until reasonably free of air bubbles.

(4) With glass at room temperature (70 - 80°F) and
the glue solution at 135-145°F., with the glass plate Perfectly Level, pour sufficient glue upon glass to deposit glue equal
to three (3) ounces of dry glue per square foot of glass area [Nine (9) ounces of liquid glue as prepared.] (or less if a smaller chip pattern is desired).

(5) Let glue solution gel firmly upon plate before moving to preliminary storage for air drying.

(6) Place plate in drying tunnel or chamber where a gentle draft of air at room temperature is blown across the glue film (70 - 80°F). Let remain until glue film becomes tough and somewhat hard. The glue film when tested with thumb nail should not cut, but should indent like hard rubber.
NOTE: At this point, ratio of glue to water, in film, will be approximately one to one half.

(7) Remove to oven type drier and dry at 125°F. After four to eight hours drying, on average, the glue film will pop off chipping the surface of the glass and creating a moderately fine sized pattern.
(With some glass a hot day will suffice.)

(8) Those particles of glue not popping off by themselves can be scraped off by a blunt spatula or wooden board. (Use Eye Protection)

(9) Masking tape is removed and glass washed to remove all traces of glass, glue, and masking tape.

The above outline, while relatively simple to follow,
is subject to a number of variations.
To duplicate results on a production basis, particularly
as to type of glass chipping pattern, it is essential that
all steps of the process be under strict control.
That such steps are difficult to control is obvious, particularly as to accurate control of the dry weight of glue deposited per square foot of glass, and the ratio of glue to water, in step (6), just before glass with air dried glue firm is transferred to oven for final drying.
A discussion of the controls and variables follows.

GLASS:
The type of glass has a bearing on the relative ease and success of chipping. A hard, flint-like glass is impossible to chip with any uniformity of chipping, unless previously sandblasted.
Some of the plate glasses will chip fairly readily
without sandblasting; but sandblasting is recommended.

GLUE CONCENTRATIONS:

The weight of dry glue per square foot of glass is the primary control. From practical considerations, choose the ratio of glue to water to give a moderate viscosity to ensure easy, even spreading, yet heavy enough such that the glue film will set to a gel in a reasonable period of time at room temperature.
For depositing three (3) ounces of dry glue per square foot of glass area by pouring methods, the minimum dry glue to water ratio is one to two.

GLASS CHIPPING PATTERN:

The glass chipping pattern as to fine, medium, and heavy cuts/size of pattern is subject to a number of variables.
The duplication and uniformity of each is dependent
on rigid control of the variables.

These Are:
(1) Glass: type, preparation of surface.

(2) Room temperature.

(3) Animal Glue -
     concentration, temperature, at application.

(4) Weight of dry glue in water deposited
       per square foot of glass.

• Minimum practical amount of glue in water
     per sq. foot of glass is 1 to 1 1/2 ounces.

• 2 to 3 ounces of glue in water applied per sq. foot of glass will give a larger chip pattern. (the results will vary by type of glass and the other variables as listed here.)

(5) Dryness of glue film at end of initial air
      drying just before placing in final dry oven.

(6) Temperature of dry oven.
 
CAUTIONS:

Wear safety glasses as the chips can come
flying off the surface with some force.

SHARP SHARDS!!
The glass chips are EXTREMELY Sharp and the odor attractive to pets as the glue is an animal by-product.
Handle the chips with care and dispose of the glass
shards in a covered container.

PHYSICAL CONSIDERATIONS:

Where a one dry glue to two parts water is used,
correct deposition of glue per square foot of glass area
is obtained if a 1/16th inch thickness of glue is applied.
This is equivalent to approximately three ounces of
dry glue per sq. foot of glass area.

Where a masking tape is used for out lining special areas,
it is essential that the tape hold fast and flat at the borderlines. Otherwise, the wet glue will seep under
the tape and leave an uneven chipped borderline.

GLUE PREPARATION:

(1) Control the uniformity of the glue concentration
at all times. Weigh out the dry glue and cold, clean water.

(2) After preliminary soaking, heat the glue in a double boiler type jacketed container or glue pot. Do not boil, overheat, or use direct heat for the glue. Use a thermometer and monitor the glue to the 135°-145°F. recommended temperature.

(3) Keep a cover on the glue kettle
       to prevent loss of moisture.

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