Inqism-02: Chart the Direction

[Inquisitor]

At times, a 3D printer does offer advantages.

Well Done Captain.

Without a 3D printer... me carving an octopus... hmmm... How's this:

[chipveres]

I'm a little slow. It's an MX because it merges attributes of an M and an X. When I first read it I thought it stood for Macgregor Experimental.

Chip V.
s/v Sand Dollar

[Inquisitor]

...Macgregor Experimental.

I kind of like that mindset better!
Half M, half top-secret X-plane.

[kmclemore]

I'm a little slow. It's an MX because it merges attributes of an M and an X. When I first read it I thought it stood for Macgregor Experimental.

Chip V.
s/v Sand Dollar

As a Miata owner, I can't help but keep thinking of the Mazda MX-5 (Miata)!

[kmclemore]

Well, I’m certainly flattered but I’m not sure what sort of advice you’re looking for. Is it about the spraying process or the materials (urethanes, thinners, etc.) or ??

Thank you Kevin.
Having never sprayed polyurethane,

1. Is it safe? - I've read paint like aircraft Imron will flat kill you without the right air gear.
2. I'm not looking for selling quality furniture grade results... just better than what I see with brushing.
3. The can recommended and I used 4 coats on this project, but the more it built-up the more wavy and brush strokes are visible.
4. Like I mentioned above, I prefer the non-yellowing of this specific product. All others I've tried - polys, lacquers, spar, varnish... etc seem to yellow and seriously change over time. This one on oak flooring never yellowed. I could put a piece of the raw wood next to it and can't tell a color difference.
5. Does spraying take a long learning curve before a Noob can get better than brushing results?
6. Since its a water based Poly, I'm assuming I just thin it with water??? How do I tell how much? - Trial and Error?
7. I got this on sale... well... because it was on-sale $9.95 and some day, I might use it. I wouldn't use it on my own car, but for a wood project, I'm game.

Wow... that's a PILE of questions.

Is it safe? Well, no, not without protective equipment, but yes, it can be with the right stuff. In general, most 1-part poly can be sprayed while wearing an OSHA respirator (note I did NOT say 'mask'). 2-part poly is much more hazardous and requires an air supply and significant breathing apparatus. Water-based acrylics don't create a real hazard at all, so a light duty respirator would be plenty.

Coats of poly (urethane or acrylic) can definitely be applied using spray, which would eliminate the brush strokes. However, to avoid clouding of the finish, always use gloss for your undercoats and your last coat can be whatever you like (gloss, semi-gloss, satin, flat, etc.). Gloss has no flattening additives and won't cloud, but non-gloss finishes have an additive to flatten the finish and when you use multiple coats it ends up being really foggy and sometimes even a bit white-ish when you're done. With oil-based polyurethanes you can apply as many coats as you like (although I'd stop at 4) but with water-based acrylic paint, I'd avoid more than two coats on darker woods since it can get a little cloudy with successive coats no matter what gloss level you use.

As to yellowing, yes, polycrylic is the way to go - I don't know of any polyurethane that will not impart some level of yellowing. That being said, that little bit of yellowing to me is quite pretty, but more importantly the urethanes are going to be MUCH better for a marine environment since acrylics aren't particularly durable in damp, hot conditions. Urethanes are available in both water-based and oil-based, but I prefer the latter - again, because of durability.

Thinning of water-based paints should be done with great care and in considerable moderation. They really don't need much thinning - they're already pretty thin - and if you add too much water the properties of the coating can be altered, causing the finish to not be what you expected. Frankly, I'd avoid thinning water-based coatings if you can.

[NiceAft]

At times, a 3D printer does offer advantages.

Well Done Captain.

Without a 3D printer... me carving an octopus... hmmm... How's this:

I just noticed; your octopus is a novempus.

[Inquisitor]

Wow... that's a PILE of questions.

Sorry... I come by my username honestly. Maybe... I should be promoted to The Grand Inquisitor


Thank you very much Kevin!

This was very clear and concise and much of this I've never read. Then again, maybe I did. These days... it is very difficult to pull the information out of the liability and marketing jargon. "Superman costume does not permit user to fly.", "Do not spray urethane in your face." OR on my can... "Diamond tough, diamond clear, diamond beautiful, patented Aluminum Oxide Nano Technology"... blah, blah, blah.

[Inquisitor]

I just noticed; your OCTOpus has nine tentacles.

Daine Bramage
Maybe one's not a tentacle?
I see... you re-edit your posts also.

[NiceAft]

I see... you re-edit your posts also.

Absolutely

[Inquisitor]

Wow... that's a PILE of questions.
...
Coats of poly (urethane or acrylic) can definitely be applied using spray
...

Kevin,

I've done a panel with the sprayer. viewtopic.php?f=8&t=28122
I have four coats on it and it looks ten times better than the brushed-on version. I used 220 grit between the first two coats and 400 grit after that and it is totally smooth except some dust that I just can't avoid. I'm not going to have a clean room. So I either have to live with the nits or sand them out and that hazes the surface a little. Frankly, its close which way I'd rather live with. After this last coat and 400 grit to remove the last specs... is there something else I can do? Is this like paint or gel-coat where I can use polish and/or wax on top of the polyurethane?

Thank you for your advice!

[NiceAft]

I have no idea what Kevin is going to say; his experience is far greater than mine, but on lacquer, I have finished with 1000 grit, and then 2000 grit.

[kmclemore]

Kevin,

I've done a panel with the sprayer. viewtopic.php?f=8&t=28122
I have four coats on it and it looks ten times better than the brushed-on version. I used 220 grit between the first two coats and 400 grit after that and it is totally smooth except some dust that I just can't avoid. I'm not going to have a clean room. So I either have to live with the nits or sand them out and that hazes the surface a little. Frankly, its close which way I'd rather live with. After this last coat and 400 grit to remove the last specs... is there something else I can do? Is this like paint or gel-coat where I can use polish and/or wax on top of the polyurethane?

Thank you for your advice!

I have no idea what Kevin is going to say; his experience is far greater than mine, but on lacquer, I have finished with 1000 grit, and then 2000 grit.

Great that it's worked out for you!

Yeah, 400 should be fine for in between coats. I generally don't advise going too much finer, unless you're working with an extremely thinned coating, because the layers need something to 'key' into so that each can lock to the next. The tiny grooves left by extremely fine papers (beyond 600) may be too small to allow the coats to key into each other properly, which could, in extreme cases, lead to de-lamination during surface stress (heat, humidity, wear, impact, etc.). If you're working with an extremely thinned coating, the grooves from 400 paper may tend to show through, so you'd probably have to go to a finer paper.

Using extremely fine papers after the job is done, in order to get a flatted finish, or in preparation for polishing, is fine, however. One can also use rottenstone for that purpose, as I often do (that process is called "French Polishing"). Before final polishing, by hand or with a machine, wait at least 30 days for the surface to cure fully.

As for preventing dust from ruining your finish, always wash brushes with soap and water and dry them thoroughly prior to use, and use a new tack cloth and air gun to remove any trace particles (and obviously work in a dust-free place!).

[Jimmyt]

Sorry I can't help on this one. Never used water-based finish on something I wanted slick. The oil-based Helmsman spar urethane can be cut and polished like an automotive finish. Don't know if you can do that with the water-based product you are using, though. Are you going to be able to see the dust particles when it's installed? You could always do a test piece, let it cure, then try and do a polish on it.

I'll warn you that once you start, you'll probably have to do all surfaces. The sheen won't match when comparing the polished surface to the sprayed only surface (in my experience).

Sounds like you and Kevin have it dialed-in.

[Inquisitor]

Sorry I can't help on this one. Never used water-based finish on something I wanted slick. The oil-based Helmsman spar urethane can be cut and polished like an automotive finish. Don't know if you can do that with the water-based product you are using, though. Are you going to be able to see the dust particles when it's installed? You could always do a test piece, let it cure, then try and do a polish on it.

I'll warn you that once you start, you'll probably have to do all surfaces. The sheen won't match when comparing the polished surface to the sprayed only surface (in my experience).

Sounds like you and Kevin have it dialed-in.

Every input is valued here.

It seems like I've used just about every type, even the oil based Helmsman spar urethane. I've used at least five or six different brands. They all yellowed and most peeled if exposed to UV. Very unsightly. I was also under the impression that oil was the best. I tried this stuff because the literature and the "expert" in the store promised - no yellowing. Its made for floors. The aluminum oxide seems to make up for its water base. It doesn't yellow and for at least six years it didn't peel whereas the oil based peeled inside of two. I swear by it now, but it does dry very fast and doesn't settle worth a tinkers' ... thus spraying seems to a requirement versus the oil based always smoothed out.

I think I'll try the polishing. I got one of those random orbitals to do the exterior... every tool has to have at least two uses before they're justified! If it doesn't work out, I sand it out and reapply another layer of poly. No harm, no fowl, no learn.

[Jimmyt]

Yes. The oil-based spar urethane does darken with time. Like Kevin, I actually like that. I've never had it flake off, but it does have a finite life.

Looking forward to seeing how your polishing works out!