Polyurethane application

[Dominic74]

Need some advice please folks...

just completing a kitchen bench top island. Timber is Rain Tree (albizia saman?) and is 2 metres long, 1 metre wide.
Sanded from 40 to 400 grit, applied sanding sealer and now ready for ployurethane coat. I have chose F&W Floor Clear single pack. I live in FNQ so humidity is rarely below 75% so this may hinder things.
I have tested a few applications of the Floor Clear on the underside and have had limited success with brush application as the brush marks remain and dont flow out very well.(probably cos it skins over at a hell of a rate!) small areas look fantastic but when an area joins up to a wet edge of an adjacent area, the brush strokes remain.
so the question is this:
What would be the best method of application? Roller? Foam brush? wipe on?
(dont have spray gear i am afraid, or access)
Will a roller introduce air bubbles? with the size of the project, how can i keep a flowing wet edge? heat the product up in a can of very hot water?

any help would be fantastic!! many thanks in advance...

[munruben]

Feast Watson have a Floor Finish Applicator and lambswool sock See Here that may suit your needs. Keeping a wet edge is essential to apply the material evenly. Might be an idea to reduce the final coat with Mineral Turps which will provide a better flow of material and give a more even finish. Always do a test piece first with your process to see how it turns out.

[soundman]

Dominic mate... are you thinning the product.

Polly behaves much better if thinned up to 10%...thin too much and it goes misty.

regardless of method...unless you are thinning you aren't in the race

Oh BTW... no pint sanding past 180..240 max... for application of polly or most film finishes for that matter......in fact sand futher, bond strength will be compromised.

I wouldn't bother resanding this time... but remember next

cheers

[Dominic74]

thanks for the advice guys..much appreciated!

i thought about thinnning but the can says the product does not need thinning....so i didnt when sealing the underside.

i am now coating the top and have thinned by maybe 20%...went on MUCH better...then only problem is that i cant control the heat and humidity..got up early saturday morning and it was 25 degrees and 85% humidity....applied one coat and was much easier to apply but was skinning over in minutes...

much happier with the result compared to non thinned product..but still way short of the result i want (brush strokes are pretty visible)..so now gonna put next coat on with a clean rag and try the wipe on approach with 20% thinned...just hope the temp comes down a bit!
thanks again!

[soundman]

Ya have to moderate your thinning......thinning will make it go off faster..... but if you get the thinning balance right....you will extend your working time.

The other thing is the brush tecnique.
have a look at the door thread in this section I posted to yesterday.

If you are game you can spray ordinary polly.

AND

if you want a realy good finish from it, try rubbing it out with 1200 wet and dry used wet then hit it with a buff and some wax....it might not be 100% gloss but ya can get a finish out of it.... but it is frustrating stuff.

cheers

[Dominic74]

yeah brush technique seems to be an issue..some areas are like glass...just like it has been sprayed..some areas are not so good.

its that fine line between working the product to an even level, but not too much so that you leave brush strokes and over-work it...i am sure if it were cooler i would have more success!

i have certainly learnt NOT to go back over it after a few minutes...those areas look awful!!

i may see if i can borrow/steal a spray gun and compressor...but feel like i need to conquer this method..smaller projects have come out perfect as the surface area is smaller and the neccesity to keep a wet edge isnt as vital as it is on a 2 metre long surface...

i hope the wipe on approach brings me more success..

[soundman]

Polly is realy frustrating stuff.

But it sounds like you are getting the hang.

Temperature and humidity effect almost all finish products more than most people realise.

you realy are looking for cool moredate humidity....Um a bit of a problem in cairns at the moment

cheers

[TP1]

I generally use Minwax "Wipe On Poly" for polyurethane finishes. Some say its just polyurethane already thinned. Maybe so, but I find its pretty foolproof and people across the globe use this product very successfully.

Oh, and I have heard 2 different theories on the final coat. One is as Manruben suggested to thin the final coat. Another suggestion was not to thin it at all. The theory being that if you sand through the final coat accidentally, poly will show the layers and it will need to be redone.

[pjt]

Hi Dom, when I was floor covering and we did a cork floor finished in poly the thing was to load up the brush as much as poss and get it onto the suface as quick as possible with no more than a couple of strokes to blend in the last brush load...on a floor is a bit different to a table with horiz and vert surfaces but some of the same principle applies, it sounds like ur having a go and working it out for yourself tho.

On my last project I wiped on the poly with a rag for the first time, I tried a few styles of rag folding, probably the best is something like they do for french polishing, u definately don't want an edge or seam in the applying bit of rag and something that is a close knit (I used tee shirt matl) anything with a course weave will leave lines, tee shirt matl will as well if the weave is in line with the dirrection of stroke. What I noticed most was u had a different sort of control of the finish, hard to explain, but if u r not happy with the brush give the rag thing a go...

Pete

[Dominic74]

thanks for the great advice guys....

will try the rag approach at the weekend early in the morning...

i guess there is always the option of polishing the top off with fine steel wool or a paste to reduce any final imperfections...

will post a pic when finished....

[soundman]

What PJT says is pretty close to the money for some applications.....particularly large flat surfaces.

If you lay it on thick and fast.....concentrate on getting it on and roughly spread...then tip it off to even it out ....AND MOVE ON......DON'T GO BACK......on the big surfaces you need to move fast and make every brush stroke count.....if it is reasonablty wet and reasonably even.. it will flow out and self level.... but all within reason


I havn't tried the wipe on application, but quite a few years ago there was quite some deal made of an article in fine wood working over wipe on application using high quality paper towel.

cheers

[Dominic74]

very true..the one area that i went over (because a bee decided to land on it and drag itself 6 inches across the wet poly) looks totally dredful...i had hoped it would melt back into itself..but no, it ended up gloopy and a different sheen too...

but i guess thats how we learn..by making mistakes!

looks like i have scored access to some spray gear now...i will try one coat using wipe on method and if thats not much good, then i will spray...

thanks again for the help!

[soundman]

If its uggly now you need to sand till you have a flat ground...if you go over the lumps and bumps will just get bigger.

Random orbit 180 or 240 gritt no finer and gently.

If you are going to spray...spray.

cheers

[pjt]

I was thinking a bit more about the wipe on with a rag method, this is only based on my own experience... but a few points.....
film thickness probably would be thinner with each coat when compared with a brush
I was able to control the tone of the finish somewhat, if I wanted it flat I could spread the poly out, I could push down onto the surface and keep a smooth even look to the finish, if u do that with a brush the brush has to be really empty, and if I wanted a bit more gloss I let the rag float and not push down as much.
The rag method allows a little more time (only a little) to go back and fix a bee walk or a run which u basically cant do with a brush unless it happens as ur applying in that spot.

One of the best things is that u just chuck the bit of rag at the end of it no brush cleaning

Pete

[Dominic74]

once again, thanks for the help..

i will be sanding back the whole lot with 240 ROS to get the lumps and brush strokes out and putting last 2 coats on via spray....will tackle wipe on method another day with a smaller, maybe less precious job...

sounds odd but the whole job seems to have 'settled out' more over the week The brush strokes seem to have melted back more.... Poly seems to be odd stuff!...

i leave it a good week between applications because the last time, i waited 3 days and when i applied the second coat it bubbled and crazed in patches. Rang the F&W tech line and they said it was because the first coat wasnt fully dry...

and more rain and 98% humidity today...hmmm