polyurethane finish still rough

[Johnny]

Hi all

I recently finished a tas oak coffee table with polyurethane but after letting it dry it still feels rough.

I have used several grades of sandpaper, 80,120, 150 and then 180 before applying the first coat. I sanded in between coats with about a 250grit wet/dry paper. I think I have applied 4 coats (at least three but probably 4), but it still feels not that smooth.

Two things - was this a good process to follow? And is there anything that i can do to make it more smooth?

Hope someone may have some thoughts

John

[durwood]

your details are unclear!!

What actual poly are you using ?
How are you applying it?

[Johnny]

I used Cabot's Cabothane Oil Based clear poly, Satin finish.
I applied using a brush (I think with synthetic bristles).

For the table-top, I dipped the brush into the poly, started the brush in the middle and then stroked the brush from the middle to the ends of the wood. I repeated this going from one side of the table to the other.

[Tex B]

Johnny,

I prefer to use a wipe on, wipe off finish, and usually sand to 400 before finishing.

From where you are, I would try this:

- Get some UBeaut traditional wax and 0000 steel wool
- Apply one coat of wax using steel wool. Rub in, let it set a few minutes, buff off
- Then put on two more coats of wax using a soft rag. Again rub on, let it sit, buff off

Should give you a smooth finish over the poly.

Tex

[Johnny]

Thanks Tex for your thoughts

If I put a wax finish as the final coat, like you suggested, would this be durable enough for a coffee table?

And where do you pick up that type of steel wool? supermarket? normal hardware store?

[glenn k]

Johnny I brushed a large surface and the estopol was too dry to spread in a least one spot every time. Used wet and dry on every coat in the end used wet and dry to leave a flat finish looks good. Now I spray its quicker and easier and no brush marks.

[Sharpasaknife]

I use sanding sealer or shellac, rubbed back with 300+ grit before all poly coatings, spraying and brushing finish with a smooth result.

[Tex B]

If I put a wax finish as the final coat, like you suggested, would this be durable enough for a coffee table?

And where do you pick up that type of steel wool? supermarket? normal hardware store?

The wax will make any spills bead up, and is water resistant. If it's damaged, a quick sand and another coat of wax will fix it. Should be no problem on a coffee table.

I bought 0000 steel wool at the hardware store, they keep buckets of it with the sandpaper at Bunnys. Should be easy to find.

Tex

[durwood]

You have made a few mistakes but as you now have 3-4 coats it is probably enough material on the table. So the advice to rub flat and wax would be a good idea, though you can still add more material but leave the existing coats a good week before you attempt more to be on the safe side or the whole lot may wrinkle up on you.

First, if you rub down a table surface always use a block to back the paper you are using to keep it flat.The grades you used on the bare timber were OK. If very rough 240 can be used to start off with for the clear but its safer to use finer (400 or finer) as suggested will take longer but you will remove less and get a smoother finish.

When you apply a finish you are setting about spreading the paint over the surface so it will flow out and level itself as a liquid. Therefore you have to have the consistancy thin enough to allow the paint to level itself out flat before it sets up and becomes too tacky to move further. If the paint is too thick from the tin it will dry out too fast so you will get a rough finish. If the brush is too course it will drag through the paint and scoop out a lot of the material preventing it flowing out enough. So you must use a good quality brush with fine hair thats why a good hogs bristle brush is usually used, though you can get nice synthetic brushes.

The paint will probably need to be thinned slightly with its thinner (turps) and the warmer the temperature the more you need to add but 10% if probably all you need to add. If its too hot ( above 28 Deg) it doesn't help its better to do it when its cooler (18 -25 DEg)

Best method always is to do a test before you launch into the actual job. For a quick idea as to how things will work get a piece of glass and try out the mixture on it first. You should be able to get an answer as to how the paint will flow out within a few minutes of applying it. If its bad wash off the material with the thinner and adjust it so it does flow out nicely for you) Usually one applys a heavy coating over a small area and then wipes with the brush (wiped off on the tin ) removing the excess while it is still very wet. Look up brush application on Gooogle or do a search here for more detailed instruction if unsure.

Next the surface must be smooth so rub previous coats flat taking out any brush marks which I assume you refer to as the rough finish. Any faults in the surface will be repeated in the next coat as the finish follows the surface. Minor marks will fill with the material but they have to be small enough for the coating to fill them up. The flatter the surface the better.

As you are placing a coating onto a surface which is then going to dry behind you it should be painted on from one side of the table and the wet edge kept with you as you progress across the surface as you need to put wet paint onto wet paint. If you start in the middle and go out to the edge the middle first part will be drying out and when you eventually get back to it it may already have set up so the paint is then trying to dissolve into the now drying finish so you will see a join.

Done with a good brush on smooth timber thinned correctly when the temperature is nice it should give a good mirror finish in 2 to 3 coats.

[joe greiner]

From my Idiot's Guide to Finishing, a Work in Progress for other idiots:

Over the years, I've learned the right way to do a few things, and the wrong way to do almost everything else.

I finished this small cedar bowl, using some of the wrong ways. I didn't keep track of the sanding; probably to 400. I gave it four light coats of spray satin polyurethane. After about a week cure, I was dissatisfied with the uneven coating. I polished the inside by hand, with EEE-Ultrashine, then 1 coat of paste wax, both buffed with paper towels. I was able to mount it on my Longworth chuck in expansion mode, to machine finish the outside, the same way. The instructions for both products advise using a clean cloth. I was too impatient to hunt down any clean cloths.

The results are a lot like the results of "romance:" When it's good, it's really good; when it's bad, it's still pretty good. I'm not suggesting cavalier ignorance of the instructions, but sometimes "perfect enough" is satisfactory.

Dimensions: 4 7/8" (125mm) diameter, 3" (75mm) high.

Joe <IG1-4.jpg

[durwood]

Joe those are real nice bowls.

Like you I to learn lots by making mistakes.

I noticed you have used pressure pack poly because of the small size of your bowls that sure makes sence.

Last year I was doing a small job and normally would use normal spray equipment and clear to finish the job I had, which was only about 2" x 3''. I was in a hurry 40 Km from work and had a clear pressure pack can so used it to seal off the surface which was not timber but black printing ink on glossy paper. I wanted to make sure the ink was sealed off so it wound not get rubbed away.

So I sprayed about four coats, not light but full wet coats. I then decided to use some 1200 W&D to smooth it back and was then going to give it one final coat as I was looking for a mirror finish.

I hardly rubbed the surface when I hit the black and stuffed up the job. I then did some experimenting and found that there was virtually no build up of clear.

The majority of the spray can contents was thinner. When you think of it it has to be the spray nozzle is extra small so the material has to be really thin and depending on the brand quality could be watered down for cost reasons. As a coating the PP clear I had was probably the worst quality I have ever seen, it lasted only a few days out in the sun.

I have access to paint testing equipment and when I checked it out 7-8 coats of the PP can left a coating less than one lacquer coat from a normal spray gun ( and you use 4-5 lacquer coats to get satisfactory coverage for an article.) Its even worse for enamel poly which I estimate the Pressure pack clear would nead 15 -20 coats to equal one that was brushed on.

So the reason you got such a poor result was probably because all the contents of the can did was to deposit not much more that a thin amount to little to get a coating on and so it was a poor result. I bet if you did another bowl and skipped the PP satin finish and just waxed you would get as good a job as you did with the wax .

[joe greiner]

The problem with the bowl was uneven absorption into the soft cedar. Sometimes I'll just put on more coats to get a better final surface. The problem with machine buffing is that it may grind away most of the coating, and still leave splotches. I guess I was lucky with this one, only my third or fourth use of EEE. The EEE and wax makes a nice surface too, without the poly.

I hope this wasn't too much of a hijack, Johnny.

Joe

[walcen]

Always make sure there is no dust floating around your job when you paint. I varnished a job outside once 'cause the mother-in-law complained about the smell, once the dust and grit dried on it my only option was to sand off and do it again. Now I just lock her in the basement with a bottle of gin.
regards,
Wal

[Johnny]

Thankyou to everyone who offered some advice. From reading what soem have said, there is a lot more to finishing wood than I realised!

For my current project I reckon i'll use some steel wool and wax as a final finish. Next time I might try some sanding sealer

Cheers to all, John

[R3R]

did you apply woodfiller to the tas oak before finishing?

tas oak is an open pored grain wood and will require filling prior to finishing or extra coats of poly before the 'orange peel' goes away

i have done guitars using tas oak and it usually requires a lot more than 4 coats (wiping on poly) and a few bouts of wet sanding in between before the surface is mirror smooth...i also don't like using filler cos i do all types of multiple staining stages and prefer to 'fill' in the pores using extra coats of poly...i also don't like sanding sealers and prefer just puttin on the poly straight away to keep guitar finish thickness down...but for coffee tables it might not be an issue and it prob is highly recommended for wood like tas oak