Definition- Bubbles on the surface of finished work. Caused by exposure to heat, volatile material under the finish, moisture in the wood, or by too frequent application of coating. Anything which causes a vapor under the film may cause blistering, often thought of as larger bubbles.
Causes of Blistering- Contamination of substrate.
- A coating drying to fast, forming a skin on the surface, trapping in solvent vapors.
- Excessively hot substrate, lacquer, environment.
- Too much lacquer applied in one coat, especially on the seal coat.
- Air being incorporated into the lacquer from equipment, excessive agitation, or excessive air pressure.
- Over catalyzed product.
Prevention of Blistering- Use clean, properly prepared substrate.
- Add lacquer retarder, increasing the dry time of a coating, and reducing skinning.
- Store and use all materials at room temperature, while keeping spray and drying areas at room temperature.
- Apply the proper amount of lacquer. Build with multiple coats.
- Apply a thin wash coat as a sealer.
- Check equipment for proper function.
- Catalyze at the correct ratio.
Possible Fixes for Blistering- Strip and refinish.
- Sand and recoat.
Note: must sand down or sanded blisters may telegraph craters.
Questions to Ask- Has the product been altered in any way?
Thinners, retarders, colorants, additives, any other additional adds to the product? - Were there any products (water based, oil based, glazes, stains)used that may have left residual material behind?
- What are the environmental conditions, both during application and cure?
- Have things changed, including equipment and personnel?
- Are the products being used compatible?
- Are the products being used from the same manufacturer?
- Was there any preliminary testing of this system before it was used on a larger scale?
- When in the finish process did you notice the problem?
- Has this problem happened before?
If so, what were the conditions at that time, especially compared to the current conditions? - Has the product been catalyzed properly?
|
