2000 grit on Poly

Page 1 of 2  
Hi. I've been experimenting with different polyurethanes for my butcher block counter tops and it looks like I'm settling on a Sherwin Williams clear poly. I want a pretty high shine, but not the tacky gloss feel and uneven "liquid" look. My understanding was that I should sand the final coat with maybe a 400 or even as low as a 220 grit, and then go up to 600 and higher depending on what kind of finish I would like. Tonight I decided to try wet sanding with 2000 grit on the clear gloss poly right off the bat instead of going through the paces of higher and higher grits (this is on a test piece). It looks to me like it does fine. I have a nice smooth finish that has a little less gloss but is smooth to the touch and I don't see any imperfections. Am I missing something on my final 2000 grit finish by doing things this way? Might it be a better finish by going something like 400/600/1500/2000?
I sanded with 2000 on one half and left the other half of the sample with the high gloss "tacky" feel. When I put a wet towel down to clean off the sanding dust I noticed that the water beaded up on the untouched poly while it layed down on the sanded part. I can understand why this might be, I suppose, with the micro abrasions on the sanded side, but I wonder if it has any impact on the resistance the finish has to liquids. After all, I'm doing all this in order to protect the wood from occasional spills.
Any comments or ideas are appreciated.
dwhite
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You're probably spending a lot more time sanding than you need to.

Try a coat of butchers wax. It'll make the surface less porous (easier to clean) and restore the beading.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hiya, I can't speak to the question at heart as I don't use the poly stuff. Have you considered other finishes that are a bit easier to repair? Kitchen countertops will no doubt see a good number of "accidents" and you may want to consider the possibility of having to re-finish/touch up areas down the road. My understanding is Poly is a very tough finish but repairing it is even tougher. Cheers, cc
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
James "Cubby" Culbertson wrote:

What finish is "easier to repair" that is going to last for any time in a wet environment with exposure to acids and bases and the occasional solvent?

--
--John
Reply to jclarke at ae tee tee global dot net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This is a commercial application and the counter will be subject to occasional water/coffee spills and I needed something that would provide the best protection from stains. The areas that will contact food will have mineral oil on it.
thanks, dwhite
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
OK, great. Now you've learned a bit about surface tension. Doesn't mean a thing as long as the film is continuous.
Points out something others are trying to say when they tell you not to use polyurethane. Any break in the surface is going to grow because moisture will use the same effect to slide between the finish and the wood, then into the wood, promoting further separation of the two surfaces.
Makes thicker better, but of course, that promotes the "liquid" look.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
George wrote:

True for any finish, but the effect that he's seeing is called a "water break free surface" and the main thing that it indicates is the the surface is free of oils, waxes, etc. Checking for water-break free is one of the steps in adhesive bonding in many critical applications in aerospace. Essentially he cleaned off any wax or oil that evolved during the curing of the finish.
I can't see where that is any reason to use a less durable finish in a situation that is going to be subject to a good deal of heavy use.

--
--John
Reply to jclarke at ae tee tee global dot net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Regardless what you call it, if you have scratches in the surface, you won't get a tight droplet, and particles like those in coffee will hide from a swift wipe like troops in foxholes.
Now your experiment in using your surface as a hot plate is another matter. "Microscopic bubbles" is a red flag. You might be evolving excess moisture from beneath, and this will break your finish from the wood..

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'd bet on uncured vehicle, that's for sure. Week or more for full cure.
For repairs You'd have to do the entire, or see the edge. You might blend it flat, but it'll show a shadow.
Maybe there is still some

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You could do that. Or spill coffee over the entire surface to even out the stain.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ha! Now there's thinking outside the box. Should I use regular or decaf?
dwhite
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No. The only reason to use more abrasive grits is to more quickly knock down areas. If your application is smooth enough that you can achieve the desired smoothness with only 2000 grit, then don't go any more abrasive - you're just making more work by doing so and removing finish for no good reason.

As long as you don't go through the finish - which is unlikely with 2000 grit, then you are not at any risk with what you see. You just don't have the same surface tension as when the scratches weren't there. If it really starts to bug you then go get a quart of automotive buffing compount (light cut) and buff it up with that. It should take the fine scratches from the 2000 right out with a bit of elbow grease.

Comments? Here?
--

-Mike-
snipped-for-privacy@sprintmail.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Am I missing something on my final 2000 grit finish by

thanks for your advice.
dwhite
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Sanding first with the very fine abrasive gives you a very smooth but not necessarily flat surface that you'd get by leveling with the heavier grits first.
AIUI surface tension is affected by the roughness of the surface so it's not at all implausible that your sanded side exhibits a lower surface tension than the rougher side.
As long as you haven't sanded through the finish, you have the same material on both sides, though not necessarily the same thickness. My gut reaction is that your finishes provide equal protection on both halves.
Norm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

isn't the flatness of the surface affected not by the grit, but by the flatness and inflexibility of whatever is behind the sandpaper? the paper would only take off the high spots if the backing was hard and already flat.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Charles Spitzer wrote:

However most people don't have the patience to flatten a surface with 2000 grit sandpaper. Sure, if it has a flat backing it will eventually get the surface flat, but you may die of old age before the job is done. The grit doesn't control flatness, but it does control cutting rate. The idea is that you start off with something that cuts fairly fast, get the surface flat quickly with that, and then use increasingly finger grits to take off the marks that the coarse grit made.

--
--John
Reply to jclarke at ae tee tee global dot net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

thanks. what if it is already flat? doesn't poly, or other oil finishes, self-level pretty well?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes, but generally not smooth flat. There will typically be lots of inconsistencies in the surface. Everything from brush strokes if you use a brush to differences from the lap if you spray it, or even orange peel. Dust finds its way in sometimes and the less than perfect surface of the wood will telegraph in the finish. All of this - or any of this adds up to a less than flat surface. Depending upon how irregular it is, you will select a grit to take it down and then progress upwards in grit to be rid of the sanding marks. With sprayed finishes it's not uncommon to be able to start no coarser than 1000 grit. Typically, you can go to 1200 or 1500 from there and then to a fast rub with a rubbing compound for a mirror finish. In essence, flat is what you want to define flat to be. For some, nothing less than a mirror finish is flat. That absolutely calls for sanding.
--

-Mike-
snipped-for-privacy@sprintmail.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.