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the mandolin
Nov. 8th, 2007 11:16 pmCyn bought a mandolin kit (quite a while ago). After taking much of the year off, we're back working on it. We're at the finishing stage. The instructions booklet says to finish according to the instructions on the varnish. Sounds easy, doesn't it?
First we had to find appropriate varnish. I got some from Stewart-MacDonald, a musical instrument builder's supply house. So Cyn spent a while building up coats of the varnish. Then we had to figure out how to polish it. The instructions talked about buffing and buffing compound. I didn't really care for that idea, since it meant buying a buffer and buffing wheels, or at least an attachment for my drill, and then several buffing wheels. And then there's all the buffing compound - several different grades, and a can of that isn't really cheap.
So I looked around and discovered precision grade sandpaper. It's precision, so the abrasive is sized properly, and it's laid on very evenly so it doesn't leave scratches. And it's soft, flexible plastic - that woven, fibrous stuff. We started out with a level sanding, with standard 320-grit paper. This was to take out all the drips and brush marks. Then 400-grit. Then 600. This is really smooth, but it's dull, and you can't see any scratches in the finish. So then you go at it with 1200-grit. 1200 starts to make it shiny. The grit is so fine that each grade of paper can only cut as deep as the abrasions left by the previous grade. So the scratches from your 400-grit, can't be taken out by the 1200 grit. I was sanding with the 4000-grit, and could see some marks I couldn't get out. So I went back down a grade, and then tried the 4000 again. The marks were still there, so I had to go back down two grades. The marks were left by the 400. I had to take them out with the 600, and then work my way back up to the 4000. I learned to always go in only one direction with the paper, but a different direction with each. I went diagonally with the 600, diagonally the other direction with the 1200, and horizontally with the 4000. This way, I knew which paper left the marks, and therefore, which paper to sand with in order to remove them.
Notice the sanding papers laid out on the workbench? They're in order, to make it easy to grab the one you need. The 400-grit is out of the picture to the right. The grey is the 600, the blue is the 1200, and the pink in her hand is the 4000-grit. That's some damn fine abrasive, so to speak. The finish is shiny, but you can still see fine scratches in it. Moving on, to the left, the "mint" colored one is the 6000-grit paper, and the lighter green one is 8000-grit. The abrasive on this paper is one micron in diameter. That's one-hundredth of a millimeter. This is really polishing paper. And it was more than once last night, that I was sanding with the wrong side of the paper.
After that, I got a (sponge) buffer for my drill, and a can of compound, for the final shine. It should be like glass. Or maybe the 8000 paper is good enough. We'll see.
First we had to find appropriate varnish. I got some from Stewart-MacDonald, a musical instrument builder's supply house. So Cyn spent a while building up coats of the varnish. Then we had to figure out how to polish it. The instructions talked about buffing and buffing compound. I didn't really care for that idea, since it meant buying a buffer and buffing wheels, or at least an attachment for my drill, and then several buffing wheels. And then there's all the buffing compound - several different grades, and a can of that isn't really cheap.
So I looked around and discovered precision grade sandpaper. It's precision, so the abrasive is sized properly, and it's laid on very evenly so it doesn't leave scratches. And it's soft, flexible plastic - that woven, fibrous stuff. We started out with a level sanding, with standard 320-grit paper. This was to take out all the drips and brush marks. Then 400-grit. Then 600. This is really smooth, but it's dull, and you can't see any scratches in the finish. So then you go at it with 1200-grit. 1200 starts to make it shiny. The grit is so fine that each grade of paper can only cut as deep as the abrasions left by the previous grade. So the scratches from your 400-grit, can't be taken out by the 1200 grit. I was sanding with the 4000-grit, and could see some marks I couldn't get out. So I went back down a grade, and then tried the 4000 again. The marks were still there, so I had to go back down two grades. The marks were left by the 400. I had to take them out with the 600, and then work my way back up to the 4000. I learned to always go in only one direction with the paper, but a different direction with each. I went diagonally with the 600, diagonally the other direction with the 1200, and horizontally with the 4000. This way, I knew which paper left the marks, and therefore, which paper to sand with in order to remove them.
Notice the sanding papers laid out on the workbench? They're in order, to make it easy to grab the one you need. The 400-grit is out of the picture to the right. The grey is the 600, the blue is the 1200, and the pink in her hand is the 4000-grit. That's some damn fine abrasive, so to speak. The finish is shiny, but you can still see fine scratches in it. Moving on, to the left, the "mint" colored one is the 6000-grit paper, and the lighter green one is 8000-grit. The abrasive on this paper is one micron in diameter. That's one-hundredth of a millimeter. This is really polishing paper. And it was more than once last night, that I was sanding with the wrong side of the paper.
After that, I got a (sponge) buffer for my drill, and a can of compound, for the final shine. It should be like glass. Or maybe the 8000 paper is good enough. We'll see.
