We talk to the pros for their tips on achieving a stellar finish
Your lead finishing guy, let’s call him Ted, is indispensable. He’s got a wealth of information stored in that brain of his from correct air dry times down to the surface prep for each type of wood your shop uses. So what happens if your finishing “go to guy” suddenly isn’t available? You’re left trying to pick up the pieces.
“What we really recommend is a written finishing schedule,” says David Kennedy, North American market director for kitchen cabinets with coating manufacturer, Sherwin-Williams, in Cleveland, Ohio. The schedule should outline all the details and specifics about the finishing process. “The finishing schedule would state the proper white wood sanding for the individual substrates before the parts come into the finishing room. It would spell out what the progression of the white wood sanding would be for oak, maple, cherry, alder — whatever the substrate may be.”
The finishing schedule also outlines things like the correct application equipment with settings. “Included would be the type of spray gun to be used with both fluid and air pressures,” he explains. From correct air dry times and oven temperatures to sealer application and sealer sander procedures to topcoat application and mixing techniques, the finishing schedule should spell it out clearly and in detail. “A written finishing schedule report gives the operator a reference in which to check if something has gone wrong,” says Kennedy.
Keep it Controlled
From how the coatings look to where and how you store them, it’s important to develop procedures and best practices, and then follow them. When it comes to a consistent finish, Kennedy suggests establishing approved colour standards. “These should be both wet and dry, so that you have a master dry colour standard as well as a stepped off working log colour panel so that each operation has a colour panel of what their operation is supposed to look like.”
Keep a quantity of the stain used to make the master dry colour standard. This stain then becomes the wet standard of a specific stain colour. With it you can check incoming batches of that stain colour verses the master wet standard. Store the master wet standard in a number of small containers. One large container could potentially get damaged if the lid was left off causing solvent evaporation and the stain to become strong in colour. “Then pour down a sample of the incoming stain on a wood substrate versus the approved wet standard — that way you can literally look at it quickly to see that the incoming stain matches before anything is spraying on the production finishing line,” says Kennedy.
A controlled environment where elements such as dust control are factored in is also important. A common mistake many shops make is failing to store the coating in a controlled environment, says Joe Spencer, Canadian Sales director at coating manufacturer Becker Acroma based in Brantford, Ont. “Typically, the storage area is outside the finishing room.” Wherever it is, it’s important to ensure the area is temperature controlled and the containers are kept off the ground.
Let it Flow
If the temperature changes the viscosity of a coating will also change. So measuring the viscosity and keeping it consistent will ensure the coating flows and dries properly. “You want to run your coating anywhere between 22 and 25 degrees Celsius,” says Spencer. Keeping the viscosity, or the thickness of a coating, consistent is critical to a good finish. In finishing terms, viscosity measures the resistance of a coating to flow. To do this a viscosity measuring cup such as Zahn #2 or Ford #4 cup is used. The specific type of cup varies depending on the type of coating used.
It’s likely your shop received a viscosity measuring cup from the finishing company it does business with. The question is how often does it actually get used? The minute it takes to use is well worth the time, says Spencer. Likewise for a moisture meter tool which gauges the amount of moisture in a substrate. “A small item like a moisture meter can save a lot of headaches,” he says. “Whether it’s a small shop, a two-man or a multinational manufacturer of furniture finishing any type of substrate, it’s putting a procedure in place to eliminate the variables that can affect the coating or the finishing of the substrate itself.”
The Nitty Gritty
Proper sanding is critical to a stellar finish. Sanding serves a number of functions including removing surface defects such as scratches, and splinters, as well as grain raise. It reduces the amount of coating needed and helps with adhesion between the coating and the substrate. The better the substrate is prepared prior to finishing, the better looking the end product. While the exact methods for surface preparation depend on the type of substrate and coating used, for best results use the proper grit sequence when sanding, advises Spencer. “You want to go up in increments of smaller grit sizes.”
A general guideline to follow when moving along in the sanding sequence is to select sandpaper that removes all the scratches from the previous grit while leaving subsequently smaller and finer scratches. Poor grit sequencing can leave deep scratches on the wood so don’t try to skip the necessary steps needed to get that smooth surface by changing the grit size too drastically. For the best adhesion, finishing should be done immediately following sanding.
An ounce of prevention
Daily housekeeping is another must. “This is one of the things that will prevent dirt and air-born particles from contaminating the finish,” says Kennedy.
Finally, it’s a good idea to follow a preventive maintenance schedule to help ensure all your finishing equipment such as the air compressors, ovens, spray guns and spray booth stays in proper working condition. “Review these things on a regular basis and that will ensure you have a clean finish,” says Kennedy.
FIFO: First In First Out
Rotate your inventory properly, advises David Kennedy, North
American director for kitchen cabinets with the Sherwin-Williams
Company in Ohio. “Use the oldest [products] before you use the newest."
