Boat Building Forum

Find advice on all aspects of building your own kayak, canoe or any lightweight boats

Re: Material: Varnish - 1200 too fine a grit betwe
By:Mike Bielski
Date: 5/28/2008, 2:19 am

One of the reasons you want to sand between coats is to level the previous coat, not just provide more surface area for the next coat to adhere. Every coat will have little dust nibs and brush marks no matter how careful you are. If you don't knock these down with sandpaper between coats, with each coat they will become larger imperfections, like the layers of a hail stone. And on each coat, you'll be adding more imperfections on top of the growing crop of imperfections from previous coats.

So- you need to knock these down, and 1200 is just too fine for the job. I like to use 320 because it's less likely to burn through the coat you're working on and into the previous coat, but 220 is faster. I also don't scrimp on quality with the sandpaper- I use the 3M gold. It's got a stearate coating which drastically reduces the chance of loading. Fresh finishes tend to be really bad about loading, so you'll actually see the return on your investment in this relatively expensive paper by the second coat of finish you sand. On curved surfaces, it also helps a lot to have a flexible backing pad for the sandpaper. They actually make them, but you can also use something like a sanding sponge that's seen better days (and had all of its abrasive removed). Also- blow, vacuum, or carefully tack rag the finish before you start in with the next coat so that you have less to sand next time.

Once you lay on your last coat, then you can hit it with 400, 600, 800, 1200, 2000, and polishing compound to bring out the shine!

m

Messages In This Thread

Material: Varnish - 1200 too fine a grit between coats?
Randy Ricchi -- 5/27/2008, 8:57 pm
Re: Material: Varnish - 1200 too fine a grit betwe
Mike Bielski -- 5/28/2008, 2:19 am
Re: Material: Varnish - 1200 too fine a grit betwe
Kudzu -- 5/27/2008, 9:31 pm