Tutorial on Glue Chipping

Glue Chipping Glass is easier to master than you might think. All that's needed are a few materials and a little experimenting. You can chip on a variety of glass such as, clear, colored cathedral or flashed glass (glue chipping on flashed glass). You can also chip bottles, jars and even mirrors.

The glue used for chipping glass is usually referred to as "animal hide glue" or "glass chipping glue" and can be purchased through most stained glass retailers It should be granular like POSTŽ Grape Nuts Cereal and is usually sold by the pound. Here is our ONLINE Shop, A1StainedGlass.com sells this glue for $49.95 (U.S.) for 5 pounds and $449.25 (U.S.) for 50 pounds, plus shipping

1 pound will generally chip between 7 to 10 square feet of glass.

Preparing glass:

The surface of the glass must be roughened up to allow the adhesion needed between the glue and the glass. This is done by sandblasting the area of glass to be chipped. To do this yourself , you need an air compressor and a sand blasting pot (either siphon or pressure pot) - or check out your local Yellow Pages under 'Sandblasting' to find someone to blast the glass for you. The sand should be at least 90 grit, higher is better. After this is done clean the glass thoroughly. Use Masking Tape to create a DAM around your on the glass. This will keep the glue

Mixing the Glue:

The type or pattern of desired chip design is dependent upon the "Glue to Water Ratio". Generally the dry glue is combined with COLD water in a ratio of 2:1 (2 parts water, 1 part glue). This is measured by WEIGHT - 1˝ oz. of glue to 3 oz. of COLD water per sq. ft. of glass. If your glass is 24"x24", this is 4 sq. ft. (remember: 144 sq. in. = 1 sq. ft.) you will need 6 oz. of DRY glue and 12 oz. of cold water. after mixing let this mixture stand for about 2 hours to absorbed all the liquid. It also helps to cover this container to hinder evaporation. This mixture will form a gelatinous (I love that word) mass.

Average Recipe:
1˝ to 2 ounces of Dry Glue per sq. ft.
3 ounces of COLD water per sq. ft.

Heat this mixture in the double boiler (DO NOT try to heat the glue container directly on a burner. This will stink tremendously!). Slowly heat this mixture to 140° - 150° F. It is important that you do not boil this mixture and that is stays between the temperate of 140° to 150° F. Stir occasionally. HEAT SLOWLY. Use a candy thermometer to measure the temperature of glue.

Applying the glue:

The glass should be clean and have a DAM around it. Place this glass on a level surface. The glue will be poured onto the glass in an even layer between 1/16th to 1/8th inch thick. If the glass is level the glue will flow to a uniform thickness on its own. You can tilt the glass to help the glue flow evenly. The glass should be room temperature. CAUTION: If your glue is too hot, it may shock the glass causing it to break.

Drying time:

The glue will go through the Initial Drying Stage, this is the first hour or so. Make sure to keep the glass level. The Preliminary Drying Stage takes between 12 to 24 hours. This is where the glue will cure and loose almost all of the liquid. Circulating the air will speed up this process. The glue should be left to dry at it's own rate, do not hurry, uneven curing may result in a poor chip pattern. Then it is time for the Secondary Drying and Chipping Stage. This is when the glue actually starts to peel or chip. The glue shrinks considerably during the total drying process. As it shrinks, it grips into the pores caused by the sandblasting and literally RIPS the top of the glass off.

Use precautions when handling glass that has a dried layer of glue.

Secondary Drying and Chipping Stage

This is when I use a small space heater to warm the glass up to around 125 degrees F. This will cause a rapid evaporation of moisture leading to curling of the glue and the chipping of the glass surface. The glass is under EXTREME stress at this point and (if necessary) should be handled very carefully. On sunny days the glass can be set in direct sunlight. This is the easiest way to get the glue to chip the glass. The chips of glue can pop off with some force, take appropriate precautions, i.e. safety glasses.
After all the glass is chipped some glue may still be left on the glass. Since the glue is water soluble, you can soak the glass with warm water and scrape off the softened glue.
If you wish a Double Chip effect. Simply repeat the steps after sandblasting. The already-chipped surface will provide enough adhesion for the glue.

Variables Effecting Chipped Patterns

The glass chipping pattern is subject to many variables. The duplication and uniformity of each is dependant on rigid controls of these variables.
Some of these variables consist of:

Glass - type and surface preparation
Room Temperature during preliminary drying stage
Glue - type, concentration, temperature at time of application
Weight of DRY glue applied per sq. ft. of glass
Dryness of glue film at end of preliminary drying stage
Temperature of drying room during chipping process

Different Glue Weights

Primary control over the chip design lies in the amount of glue to water per sq. ft. of glass.

1/2 oz. of glue per foot is the minimum. Chip will be spotty or none at all.
1 1/2 oz. of glue per foot gives the best results - Uniform chipping in usually a Fern Pattern.
2 oz. is what I usually use. This gives me a larger more Iceberg looking chip.
3 oz. of glue is economically wasteful and usually the glue is so thick it won't chip at all.

Play around with these amounts to see what you get. If you need to repeat a pattern, keep good notes for all the variables involved.

Here is a fine example of "snail" type chip.