# Advice On Removing Spray Poly Drips



## J2W2 (Dec 31, 2014)

Hi,

I'm working on my first project with spray polyurethane (rattle can). Everything has gone fine on pieces that I can lay flat. Now I'm working on one that I have to spray vertically. It's 4" oak trim all the way around a fairly large piece.

I thought everything had gone fine on my first coat, but when I went out to apply a second one, I saw that I had a line of drips, about 8 to 10 inches across, right in the center of the front trim (of course).

I was trying to apply light coats, but it looks like the poly gathered in a particularly deep piece of grain, and then created eight or so drips, about the size of a BB. Since the poly is still wet, I haven't been able to feel them to gauge how thick they are.

I don't know if it was a mistake or not, but I went ahead and applied two more light coats, each about 45-minutes apart, hoping they would "melt" the drips. That may of helped a little, but they are still there. As the poly has started to dry, they have become less noticeable, since I'm using a satin finish and they kind of shined initially.

I've researched it a little, and found advice such as lightly wet (water I assume) sanding them with a very fine sandpaper after the poly has fully set. I also saw advice on using a flat sanding block and fine sandpaper, with the hope that it just hits the raised drips.

I'd planned to do a light sand and a final coat anyway, after I let it fully cure. But I wanted to ask this forum about their advice on what's the best way to remove them without having to completely refinish the front piece?

Thanks for your help!


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## Steve Neul (Sep 2, 2011)

If you can catch runs immediately you can smooth them out with a brush or rag. If you allow it to sit until it semi-hardens it's best to let it go ahead and harden. Then take a razor blade and shave the majority of the run off. Then sand what is left with sandpaper backed with a block of wood or use one of those hard rubber sanding blocks. Be careful sanding not to sand through the finish. It would be better to leave some of the run and put another coat over it and then sand some more. Eventually when you get the finish leveled put a fresh coat on the entire area.


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## epicfail48 (Mar 27, 2014)

Razor blade to hog off most of the run, then a light sanding with some 320 or 400. Tip for next time, poly doesnt meld coats, just builds layer on layer, like an onion. For the final coat id also wipe it on, if possible. Use a 50/50 mix of poly and mineral spirits, wipe on with a paper towel. Gives a much nicer finish with less chance of runs


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## J2W2 (Dec 31, 2014)

> If you can catch runs immediately you can smooth them out with a brush or rag.


 Unfortunately, I'd set a timer for 45 minutes and went out to apply the second coat when I saw it. By then I was afraid anything I tried to do at that point would just make it worse.



> For the final coat id also wipe it on, if possible.


 I'd thought about wiping it on when I wanted something other than brushing, but I decided to try spray instead. Since the rest of the piece has been sprayed (this is just the lid I'm working on, I'll probably stick with that for consistency. But I'll have to look into wiping it on for my next project.

I took a look at it this morning, before I left for work. It actually looks fairly good. The poly is dry to the touch (I know that's only on the surface), so I was able to lightly run my fingers over it. I can barely feel the runs under my fingers. I'd mentioned in the first post that they are about the size of a BB; that would be their height and width, their depth is much less than that. I've had much worse runs when I've used a brush. They didn't do much more than just run out of the length of grain that I think created them; they are all sitting just below it, so they didn't run very far.

I also noticed that under normal light, meaning light from above, they are almost unnoticeable unless I really look for them. When I was working on the piece yesterday, I had my overhead shop light on, and a work light pointing up from below. When it's lit from below, they really show up. I believe that's because the runs are widest at the bottom and that causes shadowing when lit from below. Without that light on, I really can't see them without looking up at them from below. This part of my project will sit about waist high, so no one will be looking at it from below!

As I mentioned before, I'd still like to lightly sand the entire piece and apply at least another coat or two. It feels pretty smooth right now, but I'm sure I'll find a few dust bumps when I check out the entire piece. Steve, I may even add an additional coat to the front piece if the runs are still noticeable after that.

Based on how thin the runs are, do you think I should mess with a razor blade, or just lightly sand them down and add more poly? I've used a razor blade in the past on thick runs I've had with a brush. These are so thin I'd be worried about taking off more than I want to.

Thanks again for all your help!


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## Steve Neul (Sep 2, 2011)

If the runs are that shallow I would block sand it and apply another coat. Since the finish is barely dry it might go better to wet sand the finish. Sometimes whey you sand the run it's gooey enough to ball up and tear rather than sand. Since you are doing that well with spraying the finish I would be inclined to spray the final coat. Runs just happen to all of us especially with an oil based finish.


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## J2W2 (Dec 31, 2014)

> Since the finish is barely dry it might go better to wet sand the finish.


 Steve, you had replied to a previous post I'd made when I first started this project. I'd asked about recoat time with this spray poly, and you had said the following:




> It's called a recoat window and you better pay attention to it. 72 hours is for warm weather. In winter you better give it a full week. There are a lot of finishes that have a recoat window especially rattle can paint. What will happen if you exceed the recoat window is the dried finish that is on there now will wrinkle up like you put paint and varnish remover on it.


I assume this still holds true and I'll need to give it a week before I work on it again, even though I'm trying to repair runs? I'm in Nebraska, and we've had some crazy nice weather (mid 60s today), but that is coming to an end very soon. Snow and 20s to 30s by the weekend. My garage usually holds low to mid 40s this time of year, and I can get that into the md 50s with a couple space heaters, but that's about the best I'll be able to get until things warm up a little more.

If I do wet sand, is that just done with water? I've never wet sanded before. Do you just dip the sand paper in water to get it wet and sand, or is it more involved than that? I have "pro grade" 320 and 400 grit, which has more of a rubber backing than what's on normal sand paper, so I assume that would work for wet sanding?

Thanks!


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## Steve Neul (Sep 2, 2011)

If the directions on the can say anything like recoat within an hour or two or wait 72 hours then it has a recoat window. You would either have to follow those instructions or use a different product without the harsh solvents. 

When wet sanding I use the black "wet or dry" sandpaper and use water as a lubricant. It's an automotive paper. You can dip the sandpaper in water or if you have a clean spray bottle you can spray the surface with water. Wet sanding will make the sanding go faster and prevents the semi-dry finish from gumming up on the paper. The only bad thing is you won't be able to see what you are doing. You will have to dry it off from time to time to see where you are. I'm not familiar with the sandpaper you are referring to. If it is made to be used with water then it should be fine. Most sandpapers use a water soluble adhesive to hold the grit on and when you get it wet the grit comes off.


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## J2W2 (Dec 31, 2014)

> If the directions on the can say anything like recoat within an hour or two or wait 72 hours then it has a recoat window.


 The can specifies within 2 hours or wait 72 and lightly sand before recoating, so it definitely has a recoat window.

I just pulled up my sandpaper on the Home Depot site. It's 3M Pro Grade Precision, and says "use wet or dry, clog resistant", so I think I'm good on that.

Thanks again for all your help!


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