Sanded Through The Poly To The Paint

[godzilla]

I have two tele bodies I've painted and sprayed with minwax poly.

Multiple coats with the color (rattle cans) , with two weeks of dry time, after that I sprayed with the

minwax. Four parts poly to one part thinner. I recoated lightly in never less than 30 minutes, and

made sure it was dry to the touch. Three weeks dry time for the poly. Not optimum conditions, but

better than average for spraying.

I started wet sanding with 400 and knocked the big stuff down, then went to 600 and that's when I

saw I had sanded through and stopped.

I would like to know what I did to cause this. I suspect i did not wait long enough between coats, or

perhaps not enough product (poly).

Could I scuff the finish and apply more poly and still have a decent looking finish on these bodies?

Any suggestions or advice is greatly appreciated.

Steve

Edited July 13, 2008 by godzilla

[kpcrash]

You may be able to scuff/respray and have a decent finish - make sure you clean the body with naptha as some wet/dry papers have a silicon based lubricant embedded. How many layers did you spray? With Minwax Poly, I usually do 3x3 coats - meaning 3 coats 1/2 an hour apart every 24 hours (minwax is pretty stable) for 3 days. Also - make sure you use a sanding block and let the paper do the work being EXTREMELY careful on the edges. Depending on the size of the area sanded through, you may be able to spray some of the rattlecan paint into a jar and use a detail brush to recolor the body - let it dry completely and sand flat before clear coating. Hope this helps.

[godzilla]

Thanks for the reply. I probably sprayed a total of 12 coats on each body in one day, 1/2 hour apart. After thinking about it I believe I mixed it 3 poly and 1 thinner. Thanks for the naphtha tip as well, I would never have known....in fact I wonder if the surface may have been compromised with some body oils owing to the locations of the sand throughs, near the edge on both. I used a flat piece of tumbled marble as a sanding block.and never even got into the 1/8" round over.

On my first build I used Minwax poly shake cans, same procedure, maybe a couple of more coats, and wet sanded from 400 to 1200 one step at a time and it turned out pretty nice for a first time IMHO.

I never went through the paint so I think I'll be alright. What would the best ratio be to thin this poly using a cheap 1 stage turbine.

Thanks for any information.

Steve

[kpcrash]

The ratio seems right, but in hindsight, at that mix, you may need to up your coats to 15. I read somewhere one time that with minwax rattlecan poly, you only needed 5 coats (guess that guy was heavy handed).

[Sami Ghouri]

i did the same but in a way uglier/facepalming manner.... after refinishing a 1970's Aria ProII LP and sanding the whole thing perfectly fine, i bought this polishing compound that pretended to give an "ultra shiny surface" but it turned out to be sand paper in paste form! and i ended up sanding through the headstock and messing up the custom logo i had on (the transparency method described here).... horrible stuff.... i'll refinish it once i'm done with the rest of the guitars i have lying there....

i also tried fixing a minwax poly sandthrough..... unless u're way experienced (at least much more than me) u'll end up with an okay result but u're still gonna see it everytime u grab that guitar and feel bad about it... so i'd say refinish it if you have the heart to do so... i'm personally refinishing the whole guitar once again coz some friend of mine bumped a table edge with the body and dented the finish AND the wood =S

good luck mate!

[ihocky2]

400 grit is way heavy to start with. For your level sanding never start with less than 600 grit and that is pretty darned heavy. If you spray and get it to lay down nice and level try starting with 1500 or go straight to 2000 grit. Once you learn where to set your gun and how to get a smooth finish, final sanding takes no time even with 2000 grit. You also want to make sure that you are not spraying too far apart. You want the layers to mix into each other. Minwax poly does not melt into the previous layer, so if the layer is 100% dry, when you polish you will get witness lines as you sand or polish through the layers.