Proper Wood Varnish Spray Gun Ratio Mixing With Improper Tools

By Scott Wunder | Posted: 06/16/2014 7:00AM

 

Sometimes in life you need a tool that you don’t own, don’t have handy or don’t have any idea where it is. I have this problem a lot and it is usually closely related to the fact that I don’t put my tools back as I use them. I subscribe to the “leave it close to where it is most likely to be used next” method of organization, which somehow, always leaves a tool a long way from where it is actually needed next.

I had this same problem when setting up to spray a two-part conversion varnish finish. I had all of my supplies, but no empty cottage cheese containers to work out my ratios. You don’t have to use cottage cheese containers, but I always had some handy and had used them consistently after I figured out how high the finish should be in the container and how much catalyst to add. The mixture is actually pretty simple–one batch of finish, plus 10% catalyst.

One thing I never liked about my cottage cheese container system was that I had worked out how much I needed for a full pot on my spray gun, but beyond that it wasn’t easily adjustable. If I only needed a little finish, I didn’t have a system for figuring that out. A scale would have worked great, or even measuring cups would have been nice. Heck, anything related in any way to weights and measures would have helped. But I am never that prepared.

So, there I was, looking around the shop for empty containers and finding none, but I had a revelation. One of the containers I did find had some old finish in it, and I could see the level of the finish inside the container by looking through the white plastic, and I realized that I was just inches away from having a measuring cup, except my cup didn’t have any measurements on it. No good – right? Actually, not so bad. I could make up my own measuring system (inspired by Bill Cosby and his story about Noah, I call them cubits) and mark them on the side, if I could just find an empty container.

Then the wandering begins, looking around the shop for something that might work. Then the digging begins, as I move everything in my finishing area to try and uncover an empty container. Then the cussing begins as I still find nothing to mix the finish in before I put it in my spray cup. Then… Wait! Hold on a minute! My spray cup. That is the one and only, now very clean and very empty container in the shop, just waiting to have something put in it.

Now, I am really on to something, but I can’t see through the aluminum cup to mark my cubits on the outside. If only the cup was clear. I needed a way to see how much was in the cup without being able to see through the cup. I needed some sort of stick, something that you dip in fluids (I don’t know what I would call that thing). And, you know what would be even more awesome? If whatever I used could always be found and be something that I would never have to worry about putting away. Yes, an actual stick of wood as a dipstick. Genius.

But wait, it gets even better. Since the stick didn’t have any measurements on it, I could make my own and make a different one for each batch. I could make any adjustments I needed . All I had to do was transfer my cubit measuring system to the stick, and I was in business.

I labored a bit over my cubits and how long they would be. They couldn’t be an inch because that name was already taken. Same with a half an inch and a quarter of an inch. Any measuring system I was going to use was based on an inch and that’s just not how cubits work. Everyone knows that no one knows how big a cubit really is, so it couldn’t be based on anything that already exists. The good news for the cubits of the world is that I still can’t tell you how long they are, but luckily it doesn’t matter.

The first step was to fill up my cup with finish. With the new fancy cubit ratio measuring system it didn’t matter how much I used, just as long as it was enough to do the job. Then I walked less than two feet and grabbed the nearest, short scrap of clean wood and dipped it in the finish. The highest point on the stick to get wet was now the new cubit.

I marked the high point (cubit) on the stick with a pencil and then marked a second point 10% higher to indicate how much catalyst to add. There are two ways to figure where the 10% mark goes. The most accurate way is just to measure the length of your cubit, say 5 inches and multiply by .10, which equals .5 or 1/2″. I like this method because it’s accurate and uses just a tape measure and simple math, but it isn’t as simple as it could be. My new and improved method (though admittedly slightly less accurate) is to, by eye, divide my cubit in half, then in half again, and then in half again. At that point I have a mark that is about 12.5% of the full cubit. Then again by eye I deduct a few percentage points so I am in the 10% range, and then transfer that mark to the top side of the cubit line. It takes no tape measure and no math.

 

The new and improved, super-simplified, cubit measuring system works for any fluid mixing in a straight-sided container and is accurate (as long as you aren’t blind). It is simple simon and knocks the whole process down to a stick and a pencil. And, if I can’t find those two things buried in the shop somewhere, then I am really in trouble.


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About the Author

Scott Wunder Wunderwoods

Scott Wunder

From felling the trees through installation of the final piece Scott Wunder, owner of WunderWoods in St. Charles, MO, shares his woodworking knowledge with anyone that will talk to him about wood. Whether you want to learn about milling lumber or need help on a project, get your fill of woodworking infotainment at WunderWoods.com. Scott writes about all aspects of woodworking and specializes in finishing (mostly because no one else likes to sand). Scott can be reached at wunderwoods@sbcglobal.net. Check out Wunderwoods' website at Wunderwoods.com.

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