Stiction

[RB61]

I am building up layers of Poly and using a wooden sanding block in between every two to three applications in an attempt to create a mirror like finish. The wood is White Oak and the surface has been hand planed. As I get closer to perfection, I am running into a severe amount of suction/sticking with 600 grit w/d sandpaper.

I have never done this before-any suggestions as to how to proceed? 

Thanks

[jteneyck]

Use some water with a little liquid dish washing detergent in it as a lubricant.  Alternatively, you can use mineral spirits.  

John

[RB61]

I am sorry that I did not include that information in my post. I am using water with a little liquid soap.

[Snipe Hunter]

Let it set up longer. You have too many coats and they aren't all cured. Automotive clear does the same thing if you start sanding before everything has set, cured, out-gassed etc. Just leave it alone for a while.

You may very well have undercoats still trying to dry through your last coat.

Swirls from a ROS are caused by the same thing. Little soft or uncured bits of snot stuck in the abrasive.

[RB61]

Let it set up longer. You have too many coats and they aren't all cured. Automotive clear does the same thing if you start sanding before everything has set, cured, out-gassed etc. Just leave it alone for a while.

You may very well have undercoats still trying to dry through your last coat.

Swirls from a ROS are caused by the same thing. Little soft or uncured bits of snot stuck in the abrasive.

That could be it. Sanding seemed easier for the first few groups of coats. I may be trying to hurry the process since it seems to be taking more time than I anticipated.

Thanks

[Snipe Hunter]

I've screwed up more than one job that way. You can feel the difference in resistance wet-sanding when the abrasive loads up like that. It sort of "slips" across. You're actually digging out finish. I'm 99.99% sure it's just not set up enough to sand.

We talk about "dust free" which is the time at which dust stops sticking to it which is usually around 15 minutes. Then "Time to cut (wet-sand) and buff" which can be several hours, up to a day. This stuff all has hardeners to speed the process. Something else that helps is waiting longer between coats the 1st couple coats. Problems can arise if you lay down too many coats and the bottom coats can't dry. It can blister, get foggy looking etc.

When I do cars, I shoot one coat of clear, wait about 5 minutes and shoot the second coat. That's it. Only two coats. Three causes problems..

When I do custom bikes and need a mirror finish, I shoot one coat and wet sand and shoot it again the next day and then shoot the next coat. And wait another day again for the next coat. Lather rinse and repeat. It takes a few days to get three or four coats and that "wet" look.

[fredhargis]

I love that method for getting a mirror finish on WO, but it is slow. Waiting for the varnish to dry enough between applications takes so long I only use occasionally. Some varnish seems to take longer to cure out enough than others, at least to me.