I”m rubbing out a table top I’ve sprayed with lacquer. I’m taking it down to a satin sheen, and I’m wondering about the lacquer dust in the pores. Is it possible to flash spray the top with lacquer thinner, sort of like a light “dusting”, to dissolve the dust? I’m wondering if you can achieve the look of an oil finish, with the protection of lacquer.
Any suggestions?
Replies
creekwood,
I'm not sure I understand what you are trying to do, but you can achieve a reasonable "in the wood" look by spraying a couple light coats of laquer and rubbing it out to satin.
Rob
I guess I'm trying to get an acceptable look from where I am now. I thought I had filled the pores, but found out after spraying that I hadn't done it as well as I thought. So I'm building up the finish, and this idea came to me as a way of getting a different look that would work quicker.
Butyl acetate will do what you want. Nitrocellulose lacquer is similar to shellac in that it is a solid material dissolved in a solvent (alcohol for shellac; lacquer thinner for nitrocellulose).
The best solvents for nitrocellulose are acetate solvents and butyl or isobutyl acetate have ideal dry times. Lacquer thinners are compromise products, combining expensive oxygenated solvents like acetone, MEK, MIBK and acetates - both fast and slow evaporating types - with some cheaper hydrocarbons to keep down costs. Because of the cheaper but weak hydrocarbon solvents they use, lacquer thinners generally won't have the solvent power to re-dissolve your dried lacquer and flow it out.
Remember, though, that once you re-flow your lacquer finish the original gloss will return.
For future reference, to fill the pores you whould have used a paste wood filler or a high solids clear filler before lacquering. The low solids of lacquer - on the order of 15% solids IIRC - requires many coats and sanding in between to get a smooth surface.
Hmmm... I agree with everything you said, but I have to partially disagree about the solvents and nitrocellulose. At least I think I'm disagreeing. Maybe I misunderstood you. In any case...
I've read and been told that both Ketones (particularly MEK) and Acetates are primary solvents for nitrocellulose. My own experience bears this out as I only reduce nitro products with MEK and PM Acetate and it far and away outperforms any other solvent blend I've ever seen used with nitro.
Back in '88/'89 I worked with a touch-up and repair genius. Everything we shot there was nitro. He'd take a run or sag, block it flat and then mist a blend of MEK and PM Acetate (about 90/10) over it once or twice and the surface reflowed perfectly into a flawless repair. Ever since those days I've copied his approach and I always get the same results. I've tried both straight MEK and straight PM Acetate and of the two the MEK does the better job in my experience. Although with precat I find that adding a small amount of lacquer to the mixture helps.
You're right, you don't really disagree with me. Your recipe pairs up 90% quick-evaporating MEK with very slow and powerful PM acetate (propylene glycol methyl ether acetate) that came into use when the best ever tail solvent, Cellosolve acetate (ethylene glycol monoethyl ether), was banned as toxic. In your mix it's still the acetate that is finishing the job.BruceT
I'm still not sure if we agree or not. This all seems very esoteric and borders on being beyond my own knowledge base. But... if by "finishing" you mean that the PM Acetate is the slower flashing out of the lacquer then I agree. But if you're saying that the MEK is essentially acting as a co-solvent rather than a primary then I would point you to Russ Ramirez's essay on lacquers and solvents: http://72.14.253.104/search?q=cache:gfke6wNvysAJ:www.woodfinishingsupplies.com/Lacquer%2520by%2520Design.pdf+Lacquer+by+design&hl=en&ct=clnk&cd=1&gl=us
MEK will reflow lacquer by itself. Not as well as when combined with a Glycol Esther like PM Acetate, which I presume has to do with the other resins and plastisizers in nitro lacquers. But it does work.
I didn't mean to say that MEK is not a primary solvent for nitrocellulose, just that it is too fast evaporating to be effective in re-flow use. Slower ketones (MIBK and above)tend not to be as good solvents for nitrocellulose, but the slower esters are, so butyl acetate extends dry time a little and really slow glycol ether esters are used in small percentages to keep the film open long enough for best flow and for everything else to get out, including entrapped water vapor.BruceT
Thanks, Kevin, for the info. Real good story on what you learned a ways back. I'm going to print that and keep it in my folder for future reference. I can think of several times I could've done that.
Jerry
You're welcome, Jerry. Trust me, you'll like it. It'll seem almost like magic the first few times you do it. Everytime I demonstrate it to a new installation guy, they always just kinda stare in amazement at first.
Back to your original question... I was initially going to throw this out there but I thought Rich's first response covered some of the same ground in a round about sorta way. But for what it's worth... A buddy of mine used to paint and finish custom-made moter yachts, inside and out. There were several painter/finishers there and this one old timer would never tack or wipe off his sanding sealer dust before topcoating. He preferred to leave it in the pores as a way to help fill them without the added step of using a pore filler. I don't know how it worked out for him and I don't believe that any of the other finishers used the same technique. But... these were uber-expensive high-end yachts with the usual exotic woods on the interiors. So the results couldn't have been horrendous. I suspect that it didn't fill the pores as well as a filler would have, though.
Thanks, Kevin. I actually left some of the dust on the last coat I sprayed. I don't know if it helped fill the pores, but the coat looked fine. Seems like a good idea, you know?
I believe in paying attention to the old-timers in everything they do. If we can't learn from them, who can we learn from?
thanks again,
Jerry
I definitely agree with listening to the old timers. There is a lot that can teach you. But I don't necessarily take all of it as the gospel truth. Some of them can get very stuck in their ways and essentially reach a point where they cease to learn anything. And as a general premise I don't believe that anyone ever arrives at a pinnacle of knowledge.
Thanks, Bruce. I was wondering about the gloss returning, and that answered that. I'm going to add some flattener, and see if I get to where I want.
Next time I'll make sure I do a better job of filling pores.
thanks,
Jerry
Creekwood,
I disagree with using a lacquer solvent to get the sanding dust out of the pores. I sometimes run into this problem when I'm finishing open grain wood that hasn't been filled. But I don't get it from lacquer or shellac sanding dust, I've gotten it from rubbing compound and polishing compound abrasive left embedded in the pores.
If you use a lacquer solvent, you're going to disturb the surface of the finish, probably not in a good way. Use mineral spirits instead and a SOFT bristle shoe shine brush. It won't take too long to clean out the dust and the mineral spirits wil do nothing to harm the finish itself.
Rich
Thanks Rich. I'll try that when I'm at that stage. What I have here is from rubbing the surface flat to level it.
Jerry
Jerry,If you're leveling the surface in-between coats, just keep applying your additional coats. Each one will redisolve any lacquer dust in the pores. If you're leveling the final coat, continue up through the final abrasive grit for the amount of sheen you're after. If there is any dust left in the pores, then use a brush and mineral spirits.Rich
On the subject of lacquer, I am still in the long arduous process of applying finish to the Christmas box (lacquer over shellac). I now have 12 coats of spray-can lacquer. My test boards (same wood, same treatment) were smooth and near perfect after just 6 coats. My project is not.<!----><!----><!---->
The last 2 sprayings of lacquer had slight orange-peal appearance. Is low temperature causing a not-so smooth surface finish? Air temperature at time of application was around 45-50 degrees. I applied 3 light coats, thirty minutes apart, 24 hour dry then light block sanding with 220. Next, I repeated the 3X coats and got the slight orange peal AGAIN. Orange peal was not present when I tested the finish/ process on test board (in the 62 degree basement). Test board came out beautiful.<!----><!---->
Also, how much sanding/ leveling should be done between applications? I still have a few little shinny spots, but I'm afraid to goto flatness for rear of rubbing through (and I have sanded through in a place or two). Should the finish be sanded until it is flat (really flat) before coating again? Rich, I have read your method of recoating with shellac, gradually building the surface until the shiney valley disappear- but geez, I’m on my second can of spray lacquer and one can is supposed to cover 40 square feet. That’s a lot of finish. <!----><!---->
KB
p.s. I had to bail on the shellac- I just could not get the 4 sides, 4 top edges and 4 bottom edges without runs and streaks. I will practice this however, because I believe it will be worth it to perfect the process.....will get to see Frank Klause do it next weekend!
Keef,As you probably know, finishing is one of those skills that the universe requires you to pay dues on. You go through lots of ups and downs. Things don't work, they don't work, they don't work, the frustration sets in, then one piece goes very well and you think you've got it only to have problems again.But eventually, everything starts to gell, and it's almost impossible to make it go wrong. Why your test piece was good and the real project is having problems is hard to say. But 2 obvious things stand out - 1. using spray can lacquer, 2. room temperature. It's hard to know the quality of the lacquer mixture in a spray can and the nozzle is crude compared to the atomizing action of a decent real spray gun. The propellant may be a factor also.I have NEVER sprayed lacquer below a room temp of 72, usually a bit higher. I would never finish at the temperatures you're working at.Orange peel means the lacquer is not flowing out which could be a temperature problem (which you can control) or a mixture problem (which you can't). Or the spray nozzle or propellant may be causing it by mechanical action of the spray pattern and turbulence as the spray is hitting the surface, which could be caused by spraying too close.When spraying lacquer, after the sanding sealer, which is dry for sanding in an hour, I usually shoot 3 light coats a day, sanding the next morning. 3 days generally gets the job done.Rich
All else being equal, lacquer is always going to flow out better at lower temperatures then it will at higher temperatures. That's why lacquer manufactorers market retarding solvents but not accelerating solvents. The primary risk with spraying lacquer at lower temperatures is blushing due to the much lower dew point. Although runs and sags can also be a potential problem at low temps.
I suspect that Rich is on to something with the spray nozzle on aerosol cans thing. That's probably the primary source of the orange peel. The other issue likely in play here, which Rich also alluded to, is that aerosol cans are preloaded with hot solvents like Acetone which are going to flash off super fast, thus exasperating the nozzle issue because the material doesn't have enough time to flow out before the solvents flash off.
Also, the listed coverage rate on the spray can needs to be understood in context. I have the equipment at my work to load my own aerosol cans with whatever I wish and so I get to see the process from both ends. The reality is that contents of the aerosol cans is mostly solvents. Which means that 40 sq. ft. that the can claims is the coverage rate means 40 sq. ft. of super thin lacquer. In fact it'd have to be insanely thin to cover 40 square feet of material. The solids content (what's left when the solvents all evaporate) is super low on aerosol cans.
I think the spray can nozzle is creating turbulence ("ripples") in the overly-thinned aerosol cloud which are then "frozen" on the surface of the wood by the rapidly-evaporating solvents. That's the orange peel.
I'll bet there would be less problem at slightly higher temperature. The lower temperature is no impediment to the solvents flashing off. If there weren't such a high mix of volatile solvents, the solvents would evaporate a little slower at lower temp, allowing better flow out. But with the more volatile solvents flashing off just as quickly at 60 deg as at 70, the real problem is the lower viscosity at 60 deg, preventing flowout.
Lots of factors. Who knows which is most important? But I do know the nozzle on a spray can is crude compared to even a cheap spray gun. I have a $39 Home Depot special (a standard high pressure gun) which can lay down a film that will flow out as smooth as glass.
Rich
As you say, there are a lot of factors involved and it gets very esoteric very quickly. However, as a general rule lower viscosity is more condusive to flow out than higher viscosity because there is less resistance to flowing out. Although I think that surface tension perhaps plays a bigger role than viscosity in terms of solvent selection. One of the main things that I love about using MEK with lacquer is that it has such a very low surface tension. Which means that when the atomized particals hit the surface they are going to flatten out very rapidly.
And while I certainly agree that a 10 degree swing in temperature isn't going to alter the flash rate much, Keef mentioned 45-50 degree temps to your suggested 72+. That's enough of a difference to definitely affect flow out, all else being equal. And my experience is that the same material is going to flow better at 45 than it is at 75.
At any rate... I think we certainly agree that the nozzle on the can is the most likely culprit here.
Kevin,
That's interesting about flow out and temprature. I'll keep that in mind.
The thing to keep in mind is that temperature can potentially play a huge role in how quickly solvents flash out of the finish material. Which is why force-drying with an oven as they do in the big commercial operations works so well. You're absolutely right that small differences in temp have no appreciable effect on flash times. But with bigger differences the effect becomes noticable and even pronounced, assuming low relative humidity of course. Not in terms of dew point but rather in terms of how quickly the atmosphere can absorb the flashing gasses.
Thank you for your answers to my questions. Winter in the basement is a miserable time to spray on a finish due to the fumes.
KB
Keef,
Keep those questions coming.
Listen to what Kevin has to say about spraying and chemicals whenever you can. He's been in the finishing business a long time and is as we say "the real deal"
I've been a professional finisher for a long time and have sprayed far more lacquer than I'd care to think about and I learn from him all the time.
Peter
Just keep in mind, Keef, that context is everything. I'm good at what I do. But the fact of the matter is that my experience is almost totally in a commercial production environment. High-end piece work like what Peter does... you'd be real smart to take his advice over mine! Ditto for Steve's and Rich's and others, for that matter. They each have tons of more experience within their niche than I do. All that hand rubbing to different sheens and grain filling and stuff like that... each of those guys know more than I do about.
Trust me, when it comes to shellac and particularly French Polishing... man I'm right there with the newbies following what these guys say because I've never done it. I understand the principles and have done a bit of padding here and there. But, that doesn't mean I'm competent to give advice on it... which in fact you'll probably have noticed that I never do. Hell, until a week or so ago I thought French Polish was done with Lacquer. Shows the limits of my knowledge!
My primary motivation for commenting here, and I strongly suspect that Steve, Peter, Rich, Frenchy et al would all agree with me on this, is because when I was first learning how to finish I was surrounded by old timers who didn't want to teach anybody anything because they thought that their "secrets" were the source of their value. I was definitely perceived as a threat. So this is my little rebellion. I resented being treated like a mindless drone and so I go out of my way to try to give away what I've learned at every opportunity.
Rich,
I just read through our exchange again and I hope that I don't come across as an authority on any of this. Many of these esoteric discussions are right at the border between what I actually know and what I think I know, as I suspect is probably the case for most of us who don't have a background in organic chemistry.
That said... upon reflection I must admit that there is at least theoretical merit to what you were saying about higher temps and flow out. I'd mentioned to Peter the other day about my early days in furniture factories where lacquer was sprayed from a big commercial airless pump system and heat was used to lower viscosity instead of using solvents to accomplish the same task. The temps weren't high. I don't remember how high but they weren't real high. The pipes felt warm to the touch. The point being that the heated lacquer flowed out very, very nicely over a very short time frame which allowed us to lay on a very high build coat without having it run or sag because the lacquer cooled down quickly and it did have solvents which flashed off quickly and aided both the flow out and the ability to hang on a vertical surface.
I've heard of various schemes for either preheating lacquer before loading it into a pressure pot/cup gun or ways to apply heat to the pressure pot/cup gun to warm up whatever is in it... all as a means of more or less replicating how the furniture factory did it. I know from first-hand experience that it's a very viable approach if it's done safely and correctly. Of course back in the day we had a huge commercial Air Make Up unit on the roof which controlled both air temperature and humidity, which allowed us to calibrate the heated lacquer system in a controlled environment. It'd seem to be a much dicier proposition in an uncontrolled environment. But I've never tried it with my own equipment, so I can only guess at the difficulties one might encounter being at the mercy of ambient temps and humidity. It's one of those "a bird in the hand is worth two in the bush" kind of things. I know how to get the results I want using solvents and don't see any need to try other methods that aren't as much of a known quantity to me. Doesn't mean that my way is the only way, though.
Rich,
I value your well worded replies and the time it takes to post them. I've read many of your posts and never found you to be anything but genuine and helpful. When I post these questions, I feel somewhat like a begger, so I'm always grateful for a reply. THe time will surely come when I can add to a discussion. THanks again.
KB
Keef, Don't know if you were replying to Kevin or me, but . . . "When I post these questions, I feel somewhat like a begger, so I'm always grateful for a reply" No, no! Don't EVER say that! Don't ever be hesitant to ask or take part in a discussion. I try to share the things I have learned and experienced. Every time I get the opportunity to share, I learn something more. Rich
Kevin, I have very limited expertise with finishing materials. I've learned to spray shellac, water-borne varnish and several lacquers with really inexpensive equipment. I can do it. It works. I'm happy. There are guys here who have knowledge of chemistry, formulations and behavior of finishes and technique with really good equipment and materials that I would consider too exotic to try. Rich
This forum post is now archived. Commenting has been disabled