Dos & Don'ts: Finish Testing

The following contains industrial and manufacturing information you should know about the dos and don'ts of finish testing. Read on if you or a loved one is interested in wood maintenance, safety, and news.

Dos & Don'ts: Finish Testing
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You probably check the color and sheen of your furniture to make sure it matches what your customer is expecting — but is that all the customer is expecting from the finish? It is important to check the durability of the finish to make sure your customer doesn't find problems first.
Along with assuring correct color with a stepped panel to check the color at each finish stage and checking the sheen and clarity vs. a standard panel, the customer expects the finish to be durable enough to withstand normal use.
Durability tests are destructive so you will want to finish one or more test panels when the finish is applied to the furniture. The test panels should be made of the same wood and sanded the same as the furniture. Each finish step used on the furniture should be duplicated on the test panels with the same cure times and temperatures. It is critical to finish the test panel at the same time as the furniture to assure the same coating and application is used on both the furniture and test panels.
Testing for adhesion can be performed initially after the coating is cured. Usually let the finish cure overnight before checking adhesion to prevent any residual solvents in the finish from adhering to the tape, ruining the results. Adhesion can be checked with special tools and tape if necessary; however, a razor blade and masking tape can tell you if you have an adhesion problem or not.
Make six parallel cuts through the finish into the top of the wood about 1½ in. long and 1/8 in. apart. Then make six more parallel cuts across the original cuts to make a crosscut. Apply masking tape over the crosscut area and rub firmly; then pull the tape off. Inspect the finish to see if any of the cut squares are removed. If some of the squares are removed, it is helpful to see which finish steps adhered to the tape and which adhered to the wood. The adhesion problem is between the steps adhered to the wood and the tape.
Another quick test is the "nickel" test. Just take a nickel and drag it on edge across the wood panel. The finish should dent with the wood and not crack. This easy test checks for adhesion, hardness and flexibility.
Testing for cold checks (hot and cold checks) is a little more involved, but lets you know if the finish process yielded a finish capable of expanding and contracting with the wood the furniture is made of. Allow the test panel to cure for 10 to 14 days, and then place in a hot box at 120 degrees F for one hour. Remove and place in a freezer for one hour; then bring panel to room temperature for 30 minutes and inspect under a bright light for cracks. Cracks present are a failure. This is one cycle. Repeat for a minimum of five cycles; testing can be run for more than five cycles depending on your needs.
These are a few common tests that can be performed in your shop. More information on testing can be found by contacting organizations such as the Kitchen Cabinet Manufacturers Association (KCMA), American Wood Institute (AWI), etc.
author: By David Jackson




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