UV in the Shop #4: Fluorescent Lumber Crayons

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Blog entry by Rich posted 10-02-2019 12:57 AM 531 reads 0 times favorited 0 comments Add to Favorites Watch
« Part 3: Titebond II Fluorescent to the Rescue Part 4 of UV in the Shop series no next part

I use lumber crayons for all sorts of marking on my work, from carpenter’s triangles, to arrows showing which way is up, to simple marks that indicate which edge has been jointed so I know to put that one against the fence when I rip to size on the table saw. I make all sorts of other notes on the boards as well such as which is the hinge stile and which is the center. Even just labeling parts so there are no mistakes when I do the glue up for doors, etc… and on and on.

Although it doesn’t happen often, on a couple of occasions I’ve been bitten by finding very faint marks remaining after finishing . They really weren’t visible except in certain light, but they were there.

Recently on a cabinet build, I was installing the drawer runners inside the cabinet and wearing a headlamp to help me see. When I closed the cabinet doors, sure enough a faint up arrow was staring at me on one of the center stiles. It only showed at certain angles and the headlamp exposed it. In regular light, you really couldn’t see it, but I knew it was there. Since I’d already sprayed coats of lacquer and the door was completely finished, my only option was to sand it down to bare wood and remove the mark. No big deal, lacquer is very friendly like that and I didn’t have to sand the entire door, but it cost me time.

I went searching for a solution to ensure it never happened again and sure enough, Dixon and Markal both make fluorescent lumber crayons. I ordered the Dixon brand from Amazon and was very pleased with the result.

As you can see in the photos below, even the faintest line glows brightly under my UV flashlight. They are even brighter than they appear in the pictures. Since I like to use different colors to mean different things, I’ve already ordered other colors of crayons.

Here is a mesquite board for a small box with a triangle that will allow me to make sure that after I cut it into four pieces I can glue them up in the right order and get the grain to wrap all around:

As you can see, I really don’t need to make a dark, visible line and that helps prevent any crayon from getting down into the grain.

Here is the mark under UV:

And finally, here is the crayon itself under UV:

A pack of 12 crayons cost just over $12 on Amazon. Aside from marking on construction lumber, I’ll be using these exclusively in the future.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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