OK, holiday season's over.. back to work.
Today I wet sanded the entire tank. We're sanding over a gloss epoxy primer so we want something fairly stiff, but a little more flex to 'em than the wood blocks used for the body work. I like this 3M hard rubber block. It has just enough flex for large area curves.
We're wet sanding with 400 paper. Don't remember if I mentioned it before, but I'm also a huge fan of 3M papers. Yeah... they cost a lot more than your Harbor Freight et al papers, but they're a lot more consistent in grain and lasts a whole bunch longer. Ends up being cheaper in the long run. Use the block with light pressure in a circular motion. The idea here is to knock the gloss off the flat sides and top without cutting through the primer. Watch the primer closely. As soon as you see a slight change in color... stop. That means you're about to go through. Now double a small piece of paper and use your hand to do the same with the edges... just knock the gloss off. Use lots of water to keep the tank and paper clean. Clogged paper doesn't work very well.
Once you think you've covered the entire tank, take a clean, wet rag and wipe the entire tank down several times.
Once all the water dries, you'll be able to see all the defects. These pics don't really do it justice, they stand out like a sore thumb (toe?
)
For this pic I lightly sanded just the top. As I was sanding I immediately saw them, so I wiped it down and took the pic before I finished the whole tank.
You can also see the pinholes in the bondo. Before you re-prime, take an exacto knife and dig into the pinholes just to make sure you're not just scratching the surface and the hole is actually much bigger.
If anyone knows how to completely eliminate pinholes... I'm all ears. I always manage to get a few no matter how hard I try not to.
Once you're satisfied it's just a pinhole and not a bubble, give a light sand over 'em to knock off any sharp edges you might have made with the knife. Wipe it down again and when it's dry (or still wet) give it a good blow all over with some shop air.... clean them holes out. Once it's dry, it's time to switch to some fill primer (sometimes referred to as primer surfacer). Give it a couple light coats
just on the areas where you have defects to fix. We're just using the fill primer as a base for the glazing putty... we're not actually gonna use it as a filler.
Once it's dry, fill in all the imperfections with glazing putty... sometimes referred to as spot putty. One again, I'm sold on the 3M brand. On the tank that's on the SG, I tried to use Bondo brand glazing putty. Trust me, that stuff is horrendous. Since we're dealing with small defects, I cut down a bondo spreader to a more manageable size.
As with the bondo, you're gonna overfill all the defects slightly to account for shrinkage as it dries. The glaze is pretty finicky... if you need to add more, let the first coat dry first. Otherwise the first layer will roll up on you making a bigger mess.
The putty dries pretty quick in small layers... but I'm in no rush. I'll let it dry overnight and see where we're at. At this point you're kinda on rinse and repeat with the fill primer and glaze 'till all the defects are gone.