# Finishing Issue w Wet-sanding



## misterawesome (May 23, 2018)

I'm finishing a coffee table using wet-sanding between coats of polywhey. Here's a link to that post: https://www.woodworkingtalk.com/f8/lightening-stain-before-finish-205248/#post1995522

I've read a lot about wet sanding on this forum and elsewhere, so I'm comfortable with the process...but am having some issues getting the results I'm looking for.

The issue I'm having is streaking on the table top finish. I'm not sure if I'm over-sanding between coats, not applying enough polywhey, or perhaps over-brushing. 

The pictures here are of my third coat. I brushed on coats 1 & 2, sanding in between with 600 grit 3M wetordry. I was having similar streaking and figured some of that was coming from brush strokes. The next day (today), I wet-sanded again before putting on a third coat with a foam brush. This being a third coat, I noticed the finish was "puddling" a bit so I went over again with a few slow strokes to ensure even distribution, probably 2-3 times as a whole.

For sanding, between coats 1&2 I was sanding in a single direction. There are multiple grain directions on the veneer top but my research told me that sanding in a specific direction wasn't essential, and some recommended sanding in the opposite direction on a second pass to blend balance out marks from the first. It didn't seem like I was getting even coverage with the paper, so I decided to sand in a circular manner. I felt I got much better/even coverage and hoped that it wouldn't show when the next coat was applied. The finish is drying streaky - but not with any signs of circular sanding.

I'm using a 3M rubber sanding block, but the wet-sanding doesn't seem to be giving me the coverage I see in videos I've watched. Should I not be shy about the amount of water that goes on a poly-whey finish? Does the amount of soap matter? I have a ROS I can use but can only get my hands on 400 grit paper. 

Ultimately, I'd like to do a final rub out with a paste wax but was expecting that wet-sanding would give me a smooth finish regardless. I'm not sure if it's my brushing or sanding that is standing in the way of this by leaving me with streaks.


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## ramonajim (Jan 15, 2018)

"This being a third coat, I noticed the finish was "puddling" a bit so I went over again with a few slow strokes to ensure even distribution, probably 2-3 times as a whole."

I would venture a guess that this, combined with an insufficient volume of finish, is the source of your trouble.

I'm far from an expert, but I have finished/refinished hundreds of pieces over the years. It seems to me that no matter what product is being used as a clear top finish, if I'm not using enough product it will result in the "lack of even flow" sort of trouble you're seeing.

Sent from my LG-H910 using Tapatalk


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## Steve Neul (Sep 2, 2011)

First of all you shouldn't have been wet sanding on the table. You have to have a sufficient amount of finish on the wood before using water as a lubricant sanding. It's really unnecessary to be using 600 grit and wet sanding between coats with wood finishes anyway. A light dry sanding with 220 grit is sufficient. At that time all you are trying to do is remove the fuzz where the finish raised the grain or any dust that might have gotten in the finish. If you want to do wet sanding it's necessary to have enough finish on it that the entire wood surface has enough of a coating it's about the thickness of a plastic grocery store sack. 

What you are doing is difficult. When you brush a finish you use the softest paint brush you can find. Then you brush the finish as thin as possible with as few strokes as possible. You lay on the finish and get off of it. You certainly don't go back and brush some more. The more you brush a finish introduces air in the finish causing it to set up prematurely. The finish needs to be applied wet and allowed to sit. A paint brush makes grooves in the finish and if you allow it to sit wet it will flow back together eliminating the majority of the grooves caused by the brush. If then you are able to brush out the finish where the brush marks are barely visable and is thicker than a lawn and leaf trash bag you could then wet sand with 600 grit. Then progressively wet sand with finer and finer grit until you sand it with 1500 grit or finer paper. Then to bring the sheen back rub the finish with rubbing compound until it is finish is clear and glossy again. An auto polisher with the rubbing compound would be a lot less labor intensive. 

Most of the problems you are having could be eliminated with a sprayer. If you have sufficient compressed air a cheap HF sprayer would spray that finish where you could lightly dry sand between coats until you spray one that comes out just right and you could call it done. No need to be sanding or polishing on the final coat.


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## GeorgeC (Jul 30, 2008)

Well stated Steve.


George


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## misterawesome (May 23, 2018)

Thank you very much for the insight!! I suppose I'm still wondering where I go from here. 



Should I apply a fresh coat on top of what I've got right now, hope it fills in the brush strokes, and call it a day? Should I sand the current topcoat to remove the brush marks first, before re-applying a fresh topcoat where I follow the advice above about not going back over? I'd be happy to stop sanding (wet or dry) once I can get an even topcoat. I'm more interested in having a smooth, even satin finish than bringing out gloss.



Unfortunately, I don't have access to a sprayer, so am also wondering if I should be favoring bristle brush vs foam going forward (or is that personal preference)?


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## Steve Neul (Sep 2, 2011)

misterawesome said:


> Thank you very much for the insight!! I suppose I'm still wondering where I go from here.
> 
> 
> 
> ...


I don't like foam brushes for finishes. They tend to make bubbles in the finish and bits of the foam come off into the finish. 

From where you are if spraying isn't an option just continue brushing the finish off until you have a sufficient build to rub it out. You know they finished table tops for hundreds of years before someone invented a sprayer. You might go to a real paint store such as Sherwin Williams and see what kind of paint brushes they have. Like I've said before the softer the better. For between the coats sanding you might purchase a hard rubber sanding block and use 220 grit paper dry. The hard block will tend to sand only the high places in the finish so should tend to knock down the previous brush mark. Still if you can't get to a point where you are making minimal brush marks it will take you forever to rub out the finish when you get a sufficient build.


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## misterawesome (May 23, 2018)

I'm back with an update - some wins and some lingering frustrations. Per the advice from above, I sanded down my finish with 200 dry and reapplied several coats (4-6, of polywhey) of finish to build up a smooth satin finish without leaving brushmarks. Dust is inevitable with this project so I had some decent nibs in the final finish. I left table for 5 days to cure and set about finishing the topcoat. Here was my approach:

* Wet sanded with 600 - multiple passes left behind some ridges of gloss. Research indicated I needed to step down a leavel
* Wet sanded multiple passes (3-4) with 400 to remove remaining gloss
* Wet sanded multiple passes (3-4) with 800

I had circular sanding scratches all over the table top, but applied 2 coats of Johnson's Paste Wax thinking wax would fill in the scratches and leave with me a finished table top. This was not the case. When looking straight on in low light, the table looks great - a smooth, solid finish with a low shine. But in any light the sanding marks are still evident and with paired with the wax - the table top looks greasy.

Where have I gone wrong here? Am I over-sanding/putting on too much pressure? I was not expecting needing to sand over 1000 grit to remove brush marks. I'm more than happy with the smoothness of the finish as-is, and I'm not looking to make this glossy like an electric guitar - it's the sanding marks I'm trying to eliminate. Is the answer to do more and more sanding with higher and higher grits? 

Would I consider adding another light layer of poly and calling it a day? Would a better buffing job help me here? My goal is a smooth, satin finish.

On a side note, is there rule of thumb for how much water to sue for wet sanding? In some cases, it felt like my wetordry sandpaper was "fused" to the table as I was sanding. Is this the goal as i'm sanding? Or is that a sign to rinse the accumulated finish from the paper before continuing?


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## Steve Neul (Sep 2, 2011)

If you looked at sandpaper through a microscope it would look like gravel applied to paper. The finer the paper the smaller the grains of gravel. 800 grit is still way too coarse for what you are doing. You have to carry it all the way to 2000 grit and then buff it with an electric polisher and rubbing compound before you can rid yourself of the scratches the sandpaper makes. 

Now that you have put wax on the finish I would recommend cleaning it off with a wax and grease remover before doing any more sanding. The wax will gum up on the sandpaper creating rocks of the finish which can further scratch the finish.


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## epicfail48 (Mar 27, 2014)

If youre going for a satin finish, sandpaper isnt the way you want to go. Trying to get a consistent sheen on a finish via sanding after the fact is borderline impossible. For that, you really want to topcoat with a finish that has some form of additive in it to dull the sheen.

If youre determined to do it by hand, your best bet will be to sand up to 1500 to 2000 grit, _without skipping grits_, polish with an automotive rubbing compound to get a mirror finish, and then go back over the finish with some 0000 steel wool or a grey scotchbrite pad to dull the finish back to a satin. 

Alternately, run down to your local paint store, grab some wax remover and a bottle of flattening agent, add the later to your finish, then throw another coat on your project.


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## misterawesome (May 23, 2018)

epicfail48 said:


> If youre determined to do it by hand, your best bet will be to sand up to 1500 to 2000 grit, _without skipping grits_, polish with an automotive rubbing compound to get a mirror finish, and then go back over the finish with some 0000 steel wool or a grey scotchbrite pad to dull the finish back to a satin.
> 
> Alternately, run down to your local paint store, grab some wax remover and a bottle of flattening agent, add the later to your finish, then throw another coat on your project.


Is there much of a difference in the final product between these two methods? I'm willing to put in the work for either - but is the sanding up through the grits and finishing with a grey scotchrite pad the "scenic route" whereas a topcoat of finish being a more direct path to the same outcome? 

If I were to do the latter, would I still use a light pass with grey scotchbrite to remove dustnibs? Or would that be considered too course, and i would be better served going over with a paper bag?

Many thanks!!


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## Steve Neul (Sep 2, 2011)

The scotchbrite pad is just an abrasive like sandpaper. When you are talking about 1500 to 2000 grit it is very possible the scotchbrite pad is more coarse than the sandpaper. The idea is to polish out the abrasions in the finish and going step by step is very important. If you progress too fast you will polish out the surface leaving scratches still there. Then the glossier you get the more those scratches will show.


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## epicfail48 (Mar 27, 2014)

misterawesome said:


> Is there much of a difference in the final product between these two methods? I'm willing to put in the work for either - but is the sanding up through the grits and finishing with a grey scotchrite pad the "scenic route" whereas a topcoat of finish being a more direct path to the same outcome?
> 
> If I were to do the latter, would I still use a light pass with grey scotchbrite to remove dustnibs? Or would that be considered too course, and i would be better served going over with a paper bag?
> 
> Many thanks!!


The flattening agent will give a better result. Its nearly impossible to get a consistent satin sheen via abrasive methods. Doable, but by no means easy


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## misterawesome (May 23, 2018)

epicfail48 said:


> The flattening agent will give a better result. Its nearly impossible to get a consistent satin sheen via abrasive methods. Doable, but by no means easy


Is it fair to assume a flattening agent wouldn't be necessary if I'm using a satin finish already? Does it matter if I'm using Polywhey instead of Polyurethane?


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## epicfail48 (Mar 27, 2014)

misterawesome said:


> Is it fair to assume a flattening agent wouldn't be necessary if I'm using a satin finish already? Does it matter if I'm using Polywhey instead of Polyurethane?


A satin sheen finish will generally have the flattening agent already mixed in, so no, you wouldnt need any more of it. As for the finish compatibility, you may have to do some extra legwork to find out if brand 'x' flattening agent is compatible with your finish.

This does bring up the question of why you would be sanding a satin finish, that would cause some serious issues with finish consistency. Really, anything that isnt a gloss finish probably shouldnt be touched after the final layer is applied


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## Steve Neul (Sep 2, 2011)

misterawesome said:


> Is it fair to assume a flattening agent wouldn't be necessary if I'm using a satin finish already? Does it matter if I'm using Polywhey instead of Polyurethane?


The flattening agent is a substance which looks like baby powder in dry form. How it works is when you apply the finish it floats to the surface and interrupts the sheen. The dry coat of finish this flattening agent is very superficial. The least amount of sanding or rubbing will remove most of it so what is left is more gloss than satin. This is what makes it hard to rub a finish out to satin. To make satin where it isn't streaked is to very lightly rub it with steel wool or a scotchbrite pad. It just takes a whole lot of light rubbing to get a uniform sheen. It would be a whole lot easier to get the equipment to spray a final coat of the satin polywhey on and call it done.


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## misterawesome (May 23, 2018)

Steve Neul said:


> To make satin where it isn't streaked is to very lightly rub it with steel wool or a scotchbrite pad. It just takes a whole lot of light rubbing to get a uniform sheen. It would be a whole lot easier to get the equipment to spray a final coat of the satin polywhey on and call it done.



My girlfriend is on your side - time to wrap this up! My plan is to


Remove paste wax
Fresh coat of polywhey (maybe 2)
Lightly rub with grey scotchbrite pad, but only if necessary


Two final questions
*Should I re-sand after removing the paste wax? If so, at what grit? Should I stay with the circular sanding I've been doing on the surface or switch to go in a single pattern?
* Instead of a scotchbrite pad, would a buffing disc on a ROS be useful to remove streaks?


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## Steve Neul (Sep 2, 2011)

misterawesome said:


> My girlfriend is on your side - time to wrap this up! My plan is to
> 
> 
> Remove paste wax
> ...


If you are not going to put another coat of finish on then try not to sand it or use a scotchbrite pad either. It's really difficult to maintain satin rubbing it. It usually ends up looking like the finish is old and has been abused a lot with people dragging stuff across the finish. Your best chance of a uniform sheen is to apply a coat of finish and call it done. 

If you do end up having to sand something and rub it out you sand it through the grits and the final touch is rubbing it with a scotchbrite pad putting less than than the weight of your hand on the pad.


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## misterawesome (May 23, 2018)

Steve Neul said:


> If you are not going to put another coat of finish on then try not to sand it or use a scotchbrite pad either. It's really difficult to maintain satin rubbing it. It usually ends up looking like the finish is old and has been abused a lot with people dragging stuff across the finish. Your best chance of a uniform sheen is to apply a coat of finish and call it done.
> 
> If you do end up having to sand something and rub it out you sand it through the grits and the final touch is rubbing it with a scotchbrite pad putting less than than the weight of your hand on the pad.


Sorry - I don't think my previous post was clear. I am definitely going to put on a coat of finish and call it done. I was curious to know if, after removing the paste wax with the wax and grease remover, another quick sanding was required before applying that final coat. 

If, after applying that final coat, there are any remaining dust nibs or light brush strokes, would a buffing pad attached to ROS be sufficient to remove those minor surface imperfections without getting into sanding?

Thanks!


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## Steve Neul (Sep 2, 2011)

misterawesome said:


> Sorry - I don't think my previous post was clear. I am definitely going to put on a coat of finish and call it done. I was curious to know if, after removing the paste wax with the wax and grease remover, another quick sanding was required before applying that final coat.
> 
> If, after applying that final coat, there are any remaining dust nibs or light brush strokes, would a buffing pad attached to ROS be sufficient to remove those minor surface imperfections without getting into sanding?
> 
> Thanks!


By all means sand the finish before recoating it. There are only a few finishes that are not benefited by sanding. The finish needs the scratches created by the sanding for the finish to bond to.


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## misterawesome (May 23, 2018)

Steve Neul said:


> By all means sand the finish before recoating it. There are only a few finishes that are not benefited by sanding. The finish needs the scratches created by the sanding for the finish to bond to.


Yes, I should have known that. I was thinking the light scratches from the 800 grit wet-sand would be enough but the table is almost glass-smooth to the finish at the moment.


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## misterawesome (May 23, 2018)

Steve Neul said:


> Now that you have put wax on the finish I would recommend cleaning it off with a wax and grease remover before doing any more sanding. The wax will gum up on the sandpaper creating rocks of the finish which can further scratch the finish.


I've been having a hard time tracking down the right product for this. I struck out both a local paint store and an auto supply store. Some of the prepsols that I've seen online are specific for auto - is there a concern with those going on a poly finish? 

Alternatively, could I use mineral spirits of lacquer thinner without damaging the water-based polywhey finish?


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## Steve Neul (Sep 2, 2011)

misterawesome said:


> I've been having a hard time tracking down the right product for this. I struck out both a local paint store and an auto supply store. Some of the prepsols that I've seen online are specific for auto - is there a concern with those going on a poly finish?
> 
> Alternatively, could I use mineral spirits of lacquer thinner without damaging the water-based polywhey finish?


There are many different brands of wax and grease removers. The ones sold by automotive paint stores will work on almost any finish. It might remove some latex paint but any clear finish should be alright. Mineral spirits would be better than nothing but you won't be able to depend on the wax being removed with it. Don't use lacquer thinner. It will strip the finish off.


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## misterawesome (May 23, 2018)

Steve Neul said:


> There are many different brands of wax and grease removers. The ones sold by automotive paint stores will work on almost any finish.



I finally found a bottle of DupliColor wax and grease remover from an auto parts store and removed the wax. I gave the table a sand with 220 grit via an orbital sander to prep for final finishing (using no pressure, just light guidanced to move across the table top) . 



I'm curious as to what I'm seeing here - between the white textured bits and the smoother sections. I figured I'd ask before taking another pass with the sander for fear of sanding through the finish. The sections that look "normal" actually were places I felt the stain had built up - around the edges (esp. in the upper left of this image) where I was concerned about full coverage with my brush. But my thinking is that this would be the area that would have the scuff marks. 



Please let me know if I should keep going with the sanding or apply the fresh coats of poly to wrap this up!


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## Steve Neul (Sep 2, 2011)

To me it looks pretty much normal for a finish that has been sanded. It's like if you sanded a sheet of plexiglass you wouldn't expect it to still be clear. The abrasions caused by the sanding will cloud a finish and go away with another coat. Now if you start applying a finish and it doesn't clear up then stop and wipe off the finish.


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## misterawesome (May 23, 2018)

Steve Neul said:


> To me it looks pretty much normal for a finish that has been sanded. It's like if you sanded a sheet of plexiglass you wouldn't expect it to still be clear. The abrasions caused by the sanding will cloud a finish and go away with another coat. Now if you start applying a finish and it doesn't clear up then stop and wipe off the finish.


Thanks for the peace of mind, Steve! I'm looking to put the finishing coats on this tomorrow. As I finish this up, dust nibs will be inevitable. My condo is inherently dusty due to a high ceilings and an open floor plan. I'm on the third floor - is there any chance I'd actually encounter less airborne dust if I finish on my deck, if it's not a windy day?


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## Steve Neul (Sep 2, 2011)

misterawesome said:


> Thanks for the peace of mind, Steve! I'm looking to put the finishing coats on this tomorrow. As I finish this up, dust nibs will be inevitable. My condo is inherently dusty due to a high ceilings and an open floor plan. I'm on the third floor - is there any chance I'd actually encounter less airborne dust if I finish on my deck, if it's not a windy day?


Normally when you get dust in a finish it's coming off of your clothing. If you have been sanding you get the dust on your clothes and if falls into the finish. I don't think finishing on the deck would be better. If I did that a bug would get in the finish.


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## misterawesome (May 23, 2018)

Steve Neul said:


> Normally when you get dust in a finish it's coming off of your clothing. If you have been sanding you get the dust on your clothes and if falls into the finish. I don't think finishing on the deck would be better. If I did that a bug would get in the finish.


Good point about bugs getting stuck in the finish! I was planning to apply 1-3 thinner, final coats to cover the sanding work and get to a smooth finish. I was planning to apply two coats back to back before doing any final light sanding. Knowing that dust will be inevitable, should I do a light sand between each coat (and what grit would you recommend on a ROS)? Or should I get all three coats on and do a final light rub down? This is a satin finish, so I was going to either do a light rub with a paper bag or use a buffing pad on my ROS (with no compound added) on a slow speed to remove any light imperfections but preventing gloss (if possible).


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## Packard (Jul 27, 2018)

I use a foam brush for both oil based poly and water based poly. I have not had bubble issues. 

I read about Polywhey and from what I am reading here I think I will give it a pass.

https://www.finewoodworking.com/2008/05/01/polywhey-furniture-and-floor-finishes-review

On the downside, using a foam brush left too many bubbles; when used with dark walnut the finish left an unpleasant purple/blue tint; and cherry and oak looked a bit lifeless.


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## Steve Neul (Sep 2, 2011)

misterawesome said:


> Good point about bugs getting stuck in the finish! I was planning to apply 1-3 thinner, final coats to cover the sanding work and get to a smooth finish. I was planning to apply two coats back to back before doing any final light sanding. Knowing that dust will be inevitable, should I do a light sand between each coat (and what grit would you recommend on a ROS)? Or should I get all three coats on and do a final light rub down? This is a satin finish, so I was going to either do a light rub with a paper bag or use a buffing pad on my ROS (with no compound added) on a slow speed to remove any light imperfections but preventing gloss (if possible).


I don't have any experience with the finish you are using. All I can say is you should be able to apply the finish and be done with it without any sanding or rubbing afterwards. Perhaps you have gotten some dust in the can of finish. To be sure you might go to a place that sells automotive paint and purchase some cone strainers. The mesh is a lot finer than a household paint store would sell. I don't think it's inevitable to get dust in the finish. That problem is solvable. I have about the dirtiest place in the world to finish and I can control it. 

There is only a few finishes you don't have to sand between coats. Most require a mechanical bond and the scratches provided by sanding do that. Finishes such as lacquer and shellac literally melt into previous coats and don't necessarily have to be sanded however I sand these finishes anyway because the finish gets smoother and better with each sanding. With most finishes 220 grit is sufficient for between the coats sanding. If the finish you are using is especially thin you might use 320 or 400 grit paper.


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## misterawesome (May 23, 2018)

Steve Neul said:


> I don't have any experience with the finish you are using. All I can say is you should be able to apply the finish and be done with it without any sanding or rubbing afterwards. There is only a few finishes you don't have to sand between coats. Most require a mechanical bond and the scratches provided by sanding do that. Finishes such as lacquer and shellac literally melt into previous coats and don't necessarily have to be sanded however I sand these finishes anyway because the finish gets smoother and better with each sanding. With most finishes 220 grit is sufficient for between the coats sanding. If the finish you are using is especially thin you might use 320 or 400 grit paper.



So, help me understand something. Having previously sanded my table top, I applied 2 coats of finish. I wasn't happy with how it was looking and re-sanded with 320 and applied 2 or 3 more coats as I was trying to eliminate some brush marks. I feel like I'm stuck in a loop between not wanting to apply too thick a top coat (pooling) and applying a lighter topcoat that ends up leaving brush strokes. If I wanted to smooth out further from where I am (it's not the best pic, but you'll see the brush grooves here) - my instinct says another coat will fill in some of the brush marks - BUT if I sand before applying another coat, the cycle starts anew. Is the "ideal" to sand and then apply one perfect topcoat?


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## Steve Neul (Sep 2, 2011)

misterawesome said:


> So, help me understand something. Having previously sanded my table top, I applied 2 coats of finish. I wasn't happy with how it was looking and re-sanded with 320 and applied 2 or 3 more coats as I was trying to eliminate some brush marks. I feel like I'm stuck in a loop between not wanting to apply too thick a top coat (pooling) and applying a lighter topcoat that ends up leaving brush strokes. If I wanted to smooth out further from where I am (it's not the best pic, but you'll see the brush grooves here) - my instinct says another coat will fill in some of the brush marks - BUT if I sand before applying another coat, the cycle starts anew. Is the "ideal" to sand and then apply one perfect topcoat?


A little more than 100 years ago anyone that made a table brushed the finish on the top. You used a gloss varnish and applied coat after coat until the finish was thicker than normal. A brush will make brush marks no matter how good you are. Then to get rid of the brush marks the finish was sanded until the texture of applying the finish was sanded level. After which the finish was rubbed out to a high gloss luster. People just didn't do a satin finish like what is popular today. To create a satin finish rubbing it is extremely difficult to do and not get streaks in the finish. It takes a lot of rubbing with the lightest amount of pressure to do it. All the H you are going through trying to get the finish right on your table with a satin finish could be easily done with a coat or two if you sprayed the finish. The finish comes with flattening agents in it to create satin and spraying it eliminates the brush marks. If you have compressed air a twenty dollar sprayer from harbor freight would make your finishing work so much easier you won't know how you lived without it.


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## Pondy (Oct 17, 2018)

Sanding to 220 grit between coats will leave scratches between the coats. No matter how clean you wipe it, if you take a bright light or natural light and shine at the right angle, you can see the scratches between coats. Sand to about 1000 grit between coats. Before anyone says it, no, this will not cause adhession issues with the next coat. My father and grandfather have worked with wood their whole lives, and they prefer not to even bother sanding between coats. I have a 20 year old shelf with multiple coats of poly, no sanding in between, that I made and not a single issue with it.


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