Wood Coatings Are Often Less Opaque Than We Think
More on pre-cat and post-cat wood coatings

Wood Coatings Are Often Less Opaque Than We ThinkLast week I give you two examples of what can happen when wood coatings are used without first applying a primer. In the second story, I had learned from my earlier transgression and I made certain to tell the client to apply a primer first and then apply his color coat. But I still got several follow-up calls. The first one concerned the fact that he was a quart short and they needed another gallon of color. Then came call #2. This time the client told me that can #2 didn’t match can #1. There’s a lesson here. It’s better to have two quarts too much than one pint too little!

Knowing well that I do make an occasional mistake, I asked for wet and dry samples from both cans so that I could be certain that I fixed can #2. When that material arrived, I put both cans in the mixer and made sure that they were well agitated before I did anything. There wasn’t

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much left in can #1. While they were in the mixer, I took a look at the dry samples that he sent. Sure enough, one was whiter that the other. The whiter one came from can #1. It looked like he might be right and that I might have made a mistake in tinting.

I did spray outs from both cans. I always use a real spray-out card. If you are unfamiliar with these, they are used commonly in the auto body industry where opacity or degree of transparency is crucial. Opacity is easily judged with this card because it is printed in a black and white checkerboard pattern. If you want total opacity, you need to be sure that you can’t see the checkerboard pattern when the coating has cured. No matter what you are looking for in a coating, these cards will reveal a great deal to you. They are available from auto body paint supply houses.

In my case, when both samples were done and had cured overnight, they matched exactly and there was no trace of black or white. It took a number of coats to achieve this. You would be surprised how much it actually takes to bury those black squares!

So, why was it the client came up with different shades of his color coat when both gallons of color matched exactly? Again, as with client in my first example from last week, it all comes down to the opacity of the color coat. Often, these coatings are less opaque than we think they are. Depending upon the color, opacity issues can be extreme. That’s why you need to use a primer first. And, often the primer coat must be pristine because it is the white of the primer that helps creates the final color due to the transparency of the color coat.

Until next time…spray on!

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