Sanding between coats of poly.

[semenza]

Hi,

      I have recently been trying my ETS150/5 to sand between coats of brushed (foam) on polyurethane (oil based). I  have tried several sander speed, vac  and pad combos but am not getting good results.  If I move too fast I get big visible swirls  (as predicted), if I slow down I end up sanding through. The best seems to be super soft pad , 400 Brilliant2, sander at full, and CT at 1/3. But still not even close to good enough.  Is this a case of too aggressive a sander?  I have been considering the ETS150/3. Does anyone else do this  and what set up are you using?  There are too many possible sanders and pad , interface, abrasive combos to just start experimenting.  I mostly finish/ sand flat pieces before assembly.

Seth

srs

 

[nickao]

Seth that is one reason I hate poly. It's hard to work with. Also, it's almost impossible to repair and can make the wood look like plastic.

1) Are you sure the poly is dry enough.  Sanding between coats you should be getting a white powdery dust. And you should not be seeing any noticeable swirls.

2) Are you sure the swirls were not there before you put on the first coat of finish. If  they were you will never get rid of them.

I use my little 5" PC or the ETS  125 for in-between coats. I suspect the ETS 150/3 will be much better for this application then the 150/5 because of what I see using the little 5" sanders. I have never used the 150/3 in between coats, but have tried the 150/5 and gave up before I tried out all the sandpapers and vac adjustments.

Going right to my little PC solved the problem for me.

nickao

 

[Les]

Are you doing the sanding for bonding of coats or for finish shine?

 

[semenza]

Seth that is one reason I hate poly. It's hard to work with. Also, it's almost impossible to repair and can make the wood look like plastic.

1) Are you sure the poly is dry enough.  Sanding between coats you should be getting a white powdery dust. And you should not be seeing any noticeable swirls.

2) Are you sure the swirls were not there before you put on the first coat of finish. If  they were you will never get rid of them.

I use my little 5" PC or the ETS  125 for in-between coats. I suspect the ETS 150/3 will be much better for this application then the 150/5 because of what I see using the little 5" sanders. I have never used the 150/3 in between coats, but have tried the 150/5 and gave up before I tried out all the sandpapers and vac adjustments.

Going right to my little PC solved the problem for me.

nickao

Hi,

          I don't have the plastic problem.  I have resorted to hand sanding.  I have done the same process  a lot of times and it comes out fine with no swirls unless  I try the ETS.    The swirls are not little hidden type from the stroke pattern. They are big and blatant from the larger motion of the sander . More like uneven sweeps. Yes the dust is dry white powderery.

Seth

 

[semenza]

Are you doing the sanding for bonding of coats or for finish shine?

Hi,

  After the first coat it is to get rid of the last dust nibs as well as bonding. After that just for bonding.

Seth

 

[nickao]

I am buying a 150/3 this weekend. I will try it next week and see if it is better for between coat sanding then the 150/5. It can't be any worse.

nickao

 

[semenza]

I am buying a 150/3 this weekend. I will try it next week and see if it is better for between coat sanding then the 150/5. It can't be any worse.

nickao

Hi,

  Very cool. Thanks that would be especially helpful since you have both.

Seth

 

[Les]

I just hand sand between coats so can't help there. As far as finish, I've used Per and John Lucas' techniques with good results. Very happy with polishing results.

As easy as the Menzerna polish cuts, I would think you may need to use a higher grit than 400. A friend uses 3m lapping compound between coats. He does clean after lapping but can't remember with what for sure.

I've sure had problems with not letting coats dry enough. Weather plays a big role in my shop. Maybe the poly is not dry all the way thru and you're getting the white powder off the top and scratching a lower layer.

 

[Dave Ronyak]

Seth that is one reason I hate poly. It's hard to work with. Also, it's almost impossible to repair and can make the wood look like plastic.

1) Are you sure the poly is dry enough.  Sanding between coats you should be getting a white powdery dust. And you should not be seeing any noticeable swirls.

2) Are you sure the swirls were not there before you put on the first coat of finish. If  they were you will never get rid of them.

I use my little 5" PC or the ETS  125 for in-between coats. I suspect the ETS 150/3 will be much better for this application then the 150/5 because of what I see using the little 5" sanders. I have never used the 150/3 in between coats, but have tried the 150/5 and gave up before I tried out all the sandpapers and vac adjustments.

Going right to my little PC solved the problem for me.

nickao

Hi,

           I don't have the plastic problem.   I have resorted to hand sanding.  I have done the same process  a lot of times and it comes out fine with no swirls unless  I try the ETS.    The swirls are not little hidden type from the stroke pattern. They are big and blatant from the larger motion of the sander . More like uneven sweeps. Yes the dust is dry white powderery.

Seth

The only things I hate about polyurethane (Minwax oil-based) is 1) solvent fumes and 2) slow drying.  I usually seal the wood first with a coat of Zinsser's SealCoat (dewaxed alcohol based shellac).  Then I knock down the nibs using 220 - 320 wet or dry silicone carbide paper on a block or similar foam core sanding block.  Then poly, often slightly thinned (one capful or less of mineral spirits to 8 oz of the poly.  Fresh poly dries a lot faster than a "stale" can.  I knock this down with a foam core sanding block, ideally just after the minimum drying time (just when it does not gum up the sandpaper), but if I have to leave the work and thus it fully dries before recoating, I knock off the nibs with a sanding block, then I "scrub" it all over with one of those 3M synthetic steel wool abrasive sponge sheets to knock down the gloss which means the surface is filled with minute scratches which provide mechanical grip for the final coat of poly.  I try to be extra careful in applying that last coat to avoid any runs or missed spots.  Working smoothly and quickly and steadily while maintaining a wet edge is key, with minimal brushing as possible. Each time the brush is reloaded, it is first applied to the work a little distance forward of the previous wet edge and back brushed into that wet edge as well as forward from the point of first touching the work with the reloaded brush.  Then I just let it dry.  I use this technique for finishing of interior wood trim, but have found it works quite well on flush veneered doors, too.  Most people would be hard pressed to tell it was not sprayed.  Good lighting is important to be able to see what is happening at the workpiece as you apply the finish coats.

Dave R.

 

[Bob Swenson]

Seth, we use Behlen's Rock Hard table top varnish
slightly thinned. sand between coats with 220 wet
and finish polish with Menzerna. Behlen's is a phenolic
resin varnish that drys to a hard solvent resistant
gloss finish. Remember to use a filler on grainy wood
like oak, etc. after sealing with wax free shellac.

[attachthumb=#1]          [attachthumb=#3]    [attachthumb=#2]

Bob

 

[nickao]

Bob when you finish with the Menzerna is it just a simple buff out if you need to get rid of the little scratches  higher gloss shows in certain light angles. I am sure a bar will get them soon enough.

Nickao

 

[Bob Swenson]

Yes Nickao,  but it clears the final nibs
Costomers  are a problem when they bang on the bar for an other
beer. Look at the little ridges on the bottom of a beer bottle, bad news.
Bob 

 

[nickao]

I usually just shellac and wax, but it is not nearly as durable as laying down that phenolic resin!

Sweet Bar top, looks to nice to set a beer on it!

Nickao

 

[Bob Swenson]

Nickao--- On this bar top we pored epoxy, two coats, and then applied
4 coats of rock hard. I needed to level  it because the Elk is 1/2"
down in the bar (check my trammel post). Funny thing is that even though
Epoxy is great you still need to protect it with varnish. For boats you should
use Spar Varnish to protect the epoxy from ultraviolet light.

                          [attachthumb=#]

Bob

 

[nickao]

Nickao--- On this bar top we pored epoxy, two coats, and then applied
4 coats of rock hard. I needed to level  it because the Elk is 1/2"
down in the bar (check my trammel post). Funny thing is that even though
Epoxy is great you still need to protect it with varnish. For boats you should
use Spar Varnish to protect the epoxy from ultraviolet light.

                          [attachthumb=#]

Bob

1/2" thick, WOW! Thats what gives it that look of such depth. About 50% of my work goes in boats, but I never leave the shop and 99% goes to out of state clients so I rarely see or do the final install and finishing.

Looks really nice!

Nickao