No one wants to think about a potential finish failure. In our society where liability suits are prevalent, manufacturers must take every precaution to protect against finish failures and liability suits. Preventing a problem before it occurs or having protective safe guards in place may keep your company out of bankruptcy. Many companies are re-evaluating their product liability insurance programs. Make a resolution to review your policy now. Of equal importance is taking steps to avoid a finish failure in order to maintain your integrity as a manufacturer and preserve customer relationships. Of all finish failures AWFI has documented, approximately 70 percent of failed finishes are attributed to application related problems. The remaining 30 percent of finish failures are due to coating material problems. Of the product liability cases that end up in legal action, only 5 percent are settled in favor of the wood finishing manufacturer. In light of this statistic, the industry must position itself to better prepare to withstand any product liability issue that may develop.
I. Perform Incoming Material Audit
Wood finishers are a very trusting group of professionals. How often do you grab a pail of finishing material and use it before verifying that the color or other physical properties are within specifications? I am sure all of us finishers assume every pail of finishing material is manufactured consistently and within specified tolerances. While most coating manufacturers produce materials under very strict quality standards, errors do occur and slip through the manufacturing process undetected. However, compared to the number of gallons manufactured, the quantity of substandard materials shipped is relatively low. Even so, this does not excuse us finishers from checking our finishing materials before filling up the spray equipment. The process of verifying the quality and/or color of the coating is referred to as an incoming material audit. A simple basic audit may suffice for a small manufacturer, or a detailed in-depth chemical analysis may be necessary for a very large manufacturer. In this article, we will discuss the basics of incoming material audits.
Standard basic material audits should include these checks:
- Accuracy of color
- Viscosity of the coating
- Sheen level
- Opacity of coating if opaque
To check color, a spray out must be completed and thoroughly dried. It then is compared to a color standard under soft daylight or color corrected lighting.
To verify correct viscosity, a viscosity check must be performed with a viscosity cup. The temperature of the coating must be equal to the specified temperature in the product data sheet to accurately compare viscosity. The same type of viscosity cup must be used as specified by the manufacturer or a conversion chart must be used to calculate the correct viscosity. A plus or minus of 1 to 2 seconds of the manufacturer’s specified viscosity is normally considered acceptable.
Sheen levels may be checked with a gloss meter. In the United States, the most common instrument used to check gloss reflectance is a 60 degree gloss meter. Check with your manufacturer to see what gloss standard they use to be sure your comparison to their specified gloss is accurate. A gloss range of less than five degrees plus or minus cannot be perceived by the human eye and is normally considered acceptable. For example, a 35 degree sheen that reads 39 degrees or 31 degrees is generally still considered acceptable for a 35 degree gloss coating.
For opaque materials, an opacity check may be required to assure the titanium dioxide levels are correct to achieve the desired opacity (hiding power) of the coating. An opacity chart and draw down equipment are used to perform an accurate test. American Standard Test Methods (ASTM) has a standard opacity check method that should be followed when performing this test.
II. Follow Vender Specifications
One of the most useful tools to prevent product liability problems is the Vendor Material Specification. This written document is like an insurance policy. It describes how you are going to use the coatings in the finishing system and the properties of the coating that will be shipped to you from the coating manufacturer. It will also include details of shelf life of the coating and the expected performance properties of the finishing system. This document specifies the exact finishing schedule and includes information such as preparation of the wood, curing temperatures and dry times, and the number of wet mils to apply in each coat. The total number of allowable dry mils should also be clearly specified. The coating manufacturer must provide information about the coating. This would include viscosity, density, volume solids, sheen level, catalyzation ratios and color tolerances.
The coating system should be applied in strict accordance to the specification on your substrate and sent out for independent laboratory testing. Examples of some of the tests that should be performed include tests for moisture, adhesion, chemical resistance and heat and cold cycle tests to check for potential cracking or delamination. The National Kitchen and Bath Association (NKBA) and Architectural Wood Institute (AWI) are examples of the many organizations that set standards for acceptable test results. The results of these tests should be included in the Vender Specification. After all the expectations have been set forth in the document that are mutually agreeable to both the coating and wood manufacturers, the document will then be signed and dated by authorizing personnel from both parties. A Vender Specification document should be written for every coating system the wood finishing manufacturer uses. These documents should be sealed and never disregarded. If a finish failure occurs, all parties will refer to these documents, which may potentially be used in a court of law to determine liability.
III. Perform in-process checks and record keeping
There are several measures that can be taken during the finishing process that are very helpful to prevent product liabilities and provide useful information if a liability does occur. Before spraying, the viscosity should be checked and adjusted to the standard for spray viscosity. Periodically during the work shift, the wet mil thickness of the coating should be checked and recorded. It is also extremely important to record the batch numbers of the coatings used for each production run. The batch number is generally located on the side of the coating container. It is extremely important to record these batch numbers. When a finish failure occurs, the coating vender or test lab will request batch number information. These numbers help locate coating production records and wet samples that are vital in determining the cause of the failure. Other information that should be recorded daily is humidity, temperature, mixing ratios and any other pertinent process data.
IV. Perform post-process tests
As a final step to ensure integrity of the finishing system, several post-process checks should be performed on a regular basis. Color and sheen level tests should be performed using color control masters. The most important post- process test is coating adhesion. Both substrate adhesion (adhesion to the wood substrate) and inter-coat adhesion (adhesion to the previous coats) should be evaluated. The coating must be sufficiently cured before testing for adhesion. Check with your coating supplier for recommendations on curing times before checking for adhesion. Most coating manufacturers will also recommend periodically checking for adhesion during various time intervals in the curing process, sometimes for up to 30 days.
Conclusion
Many finishers have asked how to prevent product liability issue. The answer is that it is impossible to avoid all exposure to finish product liability risk. Wood is not a man-made product. Every tree exhibits different physical and chemical properties. We recommend that you monitor wood moisture and mineral content. Never finish product that is not within acceptable tolerances. Most wood products should range between 6 and 8 percent moisture content. Check with your coating vender for recommendations on finishing systems that have exceptionally high mineral content.
With over 25 years of experience, the most important advice I can offer is to play by the rules of proper finishing principles.
- Always allow for sufficient dry times.
- Do not apply too little or too much coating.
- Do follow all finishing supplier’s recommendations that are included in their data sheets.
- Don’t inter-mix coating chemistry
- Do strive to be consistent in application of all the finishing steps.
Using detailed quality control procedures and accurate application methods may prevent a product liability and may really help you sleep soundly at the end of the day.