wood finishing questions

tevake · 01-10-2013, 06:39 PM

I've been turning a rough cut plank of timber into a finished desk top to install in our condo in Princeville. Its been fun and is coming out pretty well, but I'm having a hard time getting the final finish I'm wanting. First off the weather has been fighting me all the way. Working an open sided structure in sideways blowing rain in tough.

So far I've got 5/6 coats of full body from the package, then two coats slightly thinned
for better brushing finish. It is looking good but not quite the final smooth finish I'm looking for. Do you think a few coats of wax could bring it to a nicer finish, and what kind of wax have folks had good results with?

The wood is Kamani, usually considered a trash wood, but my neighbor cut this about three years ago and has had it stacked out side in his yard with tarps over it.
He started using some for partition walls at his house and just sands it and coats with a quick couple coats and good enough for his purposes.

I'm shooting for more a furniture finish. But didn't try to sand flat all of the grain pattern
Cause i want the hand made look.

slodave · slodave's Garage

You didn't mention what type of finish you are using.

tevake · 01-10-2013, 06:46 PM

This is weird. I rotated the pic in Iphoto and it is correct. But when I try to post and click here to Upload a Photo it comes out sideways. Whats up with that?

slodave · slodave's Garage

Did you sand between coats and did you do a final wet sand through the different grits? Just brushing a poly on won't give you the results you want.

tevake · 01-10-2013, 06:59 PM

Thanks for touching in Dave. There were times that I was looking at the plank and thinking this wood would make a nice guitar body. Lots of charicter to the wood.
Yep have been sanding to 220 dry so far. the last couple of coat I prepped quite thuroly, to a flat surface with all brush marks sanded out then thinned to get it to flow out flat. Still getting some lap marks where one section of brushing lapps into the earlier. and holidays show up as it dries.

Cheers Richard

slodave · slodave's Garage

Poly builds on itself, so you will get those overlaps and they need to be worked on to feather things in. Lacquer for example, melts into the prior coat and to some extent does away with your problem. Though, I would use a poly finish for what you are doing as well.

The idea of sanding between coats is to knock off the ridges. Forgetting the natural pores of the wood that need to be filled and leveled out, you also have the paint brush strokes. Ideally, after each coat is dry, you knock down the ridges slightly, so that the next coat(s) fill the valleys, until things are almost flush. At the end, you really need to do a wet sand starting with 220 (since that is what you are using) and work your way up. You may have work on the areas where the brush strokes are more noticeable with the lower grits, before moving on to the higher ones. Obviously, you don't want to sand to hard in those areas or you'll go through to wood. Getting that perfect finish is not as easy as it may seem.

Wax will not help much in this situation. It's mostly used to fill the final faint scratches and provide a protective coat.

tevake · 01-10-2013, 07:20 PM

Its really close now, may try one more coat. And try to brush it out a little quicker to avoid the lap marks. Its probably silly to go crazy on this as it will be exposed to vacation rental use and may well get hard use.
So sand a bit more thru what 360 grit, 500grit? Sounds like then it should get sprayed to achieve the best finish.

Thanks Richard

slodave · slodave's Garage

I doubt any more coats will help. Unless you knock those ridges down, it'll just show up again in the next coat. I'd at least sand up to 800, but knowing me I'd go even further.

You can achieve identical results either with a brush, wipe on with a rag, or spray. In the end, it's about sanding.

Those who say they can achieve a perfect spray finish and don't have to sand, are full of it.

slodave · slodave's Garage

Also, are you using any type of sanding block behind the paper?

This is for autos, but works really well with wood too. The blue side is supposed to be the sanding side, but I'll flip it over from time to time on longer flat surfaces.

http://www.amazon.com/Motor-Guard-Buster-Terror-HT-1/dp/B0082LKLLW

tevake · 08:32 PM

OK, Dave I'll try much more prep for the next coat.
Been using a rubber sanding block and just hand sanding with the paper.
The last couple of coats I did think that I had gotten most if not all of the brushing marks out, then got more plus the lap marks with the application of the next coat.

The thinning of the poli. did help it to flow out better, but caused more of the lap marks.
Maybe I should move the piece out of the breeze to slow the drying as I do the brushing.

I'll report back after the next coat with the results.

Thanks Richard

slodave · slodave's Garage

I think you are getting brush strokes on the final coats because of the thinning. I have a feeling that it's drying too quickly. You want the finish to flow and level out as much as possible before starting to set up. And yes, the breeze is not helping. Worst case, you sand to wood and start again. Wouldn't be the first time that has happened out there and won't be the last.

Good luck!

BTW, others will have their opinions as to how to apply a finish. There's 101 ways to do this.

tevake · 08:56 PM

Bear in mind that I had done at least 6 coats of the unthinned poli all ready.
So had lots of opportunities to see the brushing with that. Plus 4/5 coats on the bottom. The material is quite thick out of the can and doesn't flow out the brush marks very well.

It definitely does flow out to a smother surface with the thinning, Its more the lap marks now. So I will move it out of the breeze for the next coat to see if that slows the drying and reduces the lap marks.

Thanks again, Richard

Nostril Cheese · 01-10-2013, 09:33 PM

Is it a open grained wood?

HardDrive · 09:48 PM

It looks like much of the larger variations from when the tree was ripped into planks are still there. You have sanded the surface smooth, but its quite a hilly surface. I don't know the wood in question, but different depths may have different grains and porous qualities. Given that the wood was under a tarp outside, it is likely also still drying out. It may be a long road to getting perfect uniformity.

HardDrive · 01-10-2013, 09:47 PM

btw, I wouldn't bother making it perfect. Its a beautiful piece, and good on you for taking the time to create it.

Hydrocket · Hydrocket's Garage

PM Sent

look 171 · 01-10-2013, 09:58 PM

Richard, Hey Dave,

What finish are you trying to achieve, gloss, semi or matte? Is a completely flat finish important or you like a bit of grain texture on the surface? Do not shake the can of poly, I am sure you are aware of that.

You might want to give this a try. Since you have so many coats of finish on there, I would suggest you try wet sanding with 220. Angle the light on the surface, it should show a completely matte finish without any grain showing. That means you sanded the top layer flush and the grain filled with the poly. Reapply using an artificial lamb's wool. I like the 6" flat applicators ( we have great result with it in the field). Do not back brush or you will increase lap marks. What's the dry time on that finish? I have heat the poly in a tub of hot water so it flow out a little better. Apply an even thin coat with little over lap on there with consistent pressure (very important). Sand off the dust particles with 320 grit paper and a little water. Reapply another thin coat and you should be done. Apply BRI wax (or Johnsons) with a 0000 steel wool lightly to knock off the fine dust particles. If you like a semi gloss finish, use rubbing compound and a random orbital polisher then wax, or just use a little more pressure with the steel wool. Make sure there's enough wax on the steel wool for lube so the steel wool do not scratch the surface.

Spraying it is the best but sometimes it isn't always doable.

I am surprise you decided not to oil and wax.

tevake · 01-10-2013, 11:04 PM

Great tips here guys, thanks.

The wood is very hard, dense, and tight grained.

The plank was cut from the near the center of the log and encludes the part just under the bark. That is the front edge, with the lighter colored wood. The plank was originally 6+ inches wider and 4' longer than now. And took two guys to move around, and is still quite a load for me to move.

I kept the shape of the natural edge for interest. There was quite a bit of insect damage there so I sanded most of the chewed parts off trying to keep the shape.

Also the milling was quite rough. with the thickness gaining about 3/4 " from one end to the other.. I did try to fair out some of the undulations of the surface, but not completly. As I mentioned the goal was to keep the hand worked look in the piece. Not to create a machine finished look. But believe me there were many hours with the power sander, to get through all the weathered rough surfaces. That was fun as the color and beauty of the grain appeared..

The epoxy filled cracks you see at one end opened quite a lot more than it was, once the solid end was cut off. Requiring it to be refilled after it had lost the tension that was causing it to split. It seems to have stablized now. And is filled all the way through.

Look 171, I have been doing the application with brushing one way, with a nice Purdy brush.I've never seen the lams skin applicator that you mention, I'll check at the hardware store. That is not the fine roller on the whizzy, that you are talking about, is it?
Glad to hear your suggestions of the steel wool with wax. The finish material I've been using is satin finish so should be happy with some gentle working of the surface. Since I don't have a clean indoors spot to work there will unavoidably be some contaminates on the finish.

So I'm looking to do much more prep for the next coat, and move out of the wind flow to help with ease of application.

I'll let you all know how it goes on.

Cheers Richard

look 171 · 01-10-2013, 11:17 PM

this thing. Lambswool Applicators - BLICK art materials not a roller but a pad. they make em' 6-8" long. Best for your application imo.

We use the synthetic ones because it is cheaper and mainly for touch up work. We spray to get betteer finish even when we are doing touch up work but sometime isn't always possible inside someone's home.

look 171 · 01-10-2013, 11:26 PM

Satin finish you say? That's even easier. Go over the whole thing with wet 220. Then apply two thin coats and ssand between coats with 320. On the last coat, wet sand with 600 grit lightly, and I mean lightly, to remove the slight lap marks from the lamb's wool. Use no backing pad because your board isn't completely flat due to the lack of power plane and sanding. Wipe dry and check for lap marks. If you are satisfy(it will be a little dull), use steel wool and wax and rub like hell to achieve stain finish. Try rubbing with wax on sample first. BRI was is tough and you can achieve a pretty good low sheen with just a steel wool. You might try 000 steel wool for a little less shine.