Fine chip pattern
To achieve a chip pattern that most closely duplicates the pattern obtained by animal hide glue a coating weight of between 0.6 and 0.85 grams/in2 is recommended. This coating weight would translate to a wet coating thickness of about 50 mils. These weights should be reduced if areas greater than 2 ft2are being chipped. If very small areas (less than 2 in2) are to be chipped a greater coating weight might be required.
Figure 2: Fine Chip Pattern
Normally the adhesive will generate enough internal stress to self chip: no action is required. Chipping should occur within 45 minutes. Sometimes, when using these coating weights it becomes necessary to initiate the chipping process by lightly striking the cured adhesive with a razor knife.
This should be done very cautiously as a great deal of stress will be present in the adhesive. It may be necessary to scrape the surface of the chipped area with a razor blade to assure all glass and adhesive has been removed.
Large chip pattern
To obtain a pattern that is similar to double or triple glue chipped glass a coating weight of between 1.0 and 1.5 grams/in2 is used. This coating weight would translate into a wet film thickness of about 75 mils. Because of the heat and stress generated by this amount of adhesive, these coating weights are not recommended for areas greater than 2 ft2.
Figure 3: Large Chip Pattern
This high coating weight typically does not require any initiation to begin the chipping process; enough stress is formed inside the cured adhesive film to selfinitiate the chipping process.
Selfinitiation should occur within 30 minutes of UV curing the adhesive. Extreme care should be taken should chip initiation using a razor knife be considered for large areas with a high coating weight. There will be a great deal of stress in the adhesive and there is a very real chance that the glass will shatter. It is not uncommon for a small amount of adhesive to be firmly stuck to the extreme edge of the chipped area.
This adhesive might even be extremely sticky. This material should be removed using a razor. As with the lower coating weight, it might be necessary to scrape the surface of the chipped area with a razor blade to assure all the glass and adhesive has been removed.
Curing the adhesive
QuickChip88 and QuickChip88Gel must be cured using UV light of suitable intensity. The UV energy available from black lights is not sufficient for use with QuickChip88 or QuickChip88Gel.
A wide range of UV-curing equipment is available that is suitable for glue chipping with QuickChip88 and QuickChip88Gel. The amount of time required to cure QuickChip88 and QuickChip88Gel depends upon the energy output of the lamp and how close the adhesive is to the light source.
As a minimum a UV lamp capable of 50mW/cm2 fitted with a parabolic reflector (flood type lamp that generates collimated light) is recommended. With most UV flood lamps an exposure of 1 to 3 minutes is required to fully cure the adhesive. Because relatively thick films of adhesive are being UV cured there will be a great deal of heat produced; this is normal for this process. There will also be some gases liberated upon curing. It is recommended that curing be conducted in an area with good ventilation.
The chipping process
As the adhesive cools it becomes harder and great stress is built up within the film. Eventually the stress fractures the adhesive film. The adhesive has enough adhesion to the sandblasted glass that when the film does shatter pieces of glass are pulled from the surface of the part being chipped.
Figure 4: Cured Adhesive after Fracturing
Chipping normally occurs within 30 to 45 minutes. Usually no action is required to bring about chipping. As mentioned in previous sections it might be necessary to initiate chipping by lightly striking the cured adhesive film with the tip of a razor knife.
After the adhesive has fractured it is recommended that the part be allowed to continue to cool for an additional 30 minutes. Most of the fractured adhesive should be easy to remove. It is common for the adhesive on the edges of the piece to be more difficult to remove.
If the part has been masked as in Figure 4 the edges are easily removed: a razor knife can be used to remove the masking tape and cured adhesive. The finished piece is 8 inches by 11 inches. A coating weight of 0.89 grams/in2 was used.
|
