That’s the best title I could think of ….
This isn’t so much about finishing but about finishes. Lacquer specifically.
I opened a gallon can of it today that had been sitting around for quite some time. There was quite a bit of a thick pale mily precipitate on the bottom of the can. Pouring most of the topping off it was easy to get whatever this is back into suspension and go about my business.
The question is, what is it that separates out from the vehicle? The top part was practically water clear with a slight yellow brown cast.
Just one of life’s unexplained mysteries I hope to have explained.
Replies
The gunk at the bottom of the can is the matting agent-- usually silica. There should be none in gloss, a fair wodge in the range of satin sheens and a hefty dollop in matte.
Sometimes you can 'cheat' matte and satin finishes into becoming gloss when the matting agent has settled out like this by gently stirring only the top of the liquid to mix up the clear elements and decant this off leaving the silica at the bottom.
And if a gloss formulation of a product is too glossy and the satin (or matte) of the same manufacturers version of the polish is too flat you can stir both up and add a little of the satin to the gloss to knock off the sheen a bo'hair or two, or more if desired.
If you're a spray gun and pressure pot user (or better and safer a low pressure pump user) and you leave lacquer in the pot overnight or longer between uses you need to stir up the contents of the container to get the sheen back up to its designed level. The first 20-30 seconds of spraying even after this will give you the wrong sheen as the stuff in the line clears through. Slainte.
Richard Jones Furniture
Edited 10/25/2005 3:58 am by SgianDubh
I'm curious about the salutation: slainte.
QS, short for sliante bheatha, gaelic for 'good life' which is kind of like your good health, cheers, bottoms up, here's mud in your eye, all the best, etc.. The two words together are pronounced slanjuh var or thereabouts.
Incidentally, uisge bheatha pronounced roughly oosga var means water of life. I'll let you work out what the 'water of life' in its anglicised form is, but if you do I'll take a double, ha, ha-- ha, ha, ha. Slainte.Richard Jones Furniture
And may ye get to heaven before the devil knows..........I'm some fraction Irish and my name is Brady, so I appreciate your response. Also enjoyed your home page and the beautiful work therein. Makes we wonder if I spent full time at the craft if I would make better work, or just more of the same. You obviously made better work. See you around the forum...
Got a question maybe you can help me with. I'm trying to locate some Pre-Christian Celtic art reproductions. They can from either the British Isles, or France. Pre-Roman would be perfect. Anywhere up to about 200 BCE. Subject doesn't matter. Would you happent to know of any contacts?
Thanks,
TomWhat if Schrodinger's cat has nine lives?
Thank you, Richard for the explanation. It is as I had presumed but wasn't sure if there was something in the precipatate that was important to the over all performance (durability, drying time, etc.) of the material. I'll not worrry about getting all that goop back into suspension, just make sure there aren't any clump floating around in the cup. I usually rub out my lacquered pieces with 0000 steel wool anyway so gloss isn't the biggest factor.Cead Mille Failte
Edited 10/26/2005 11:42 am ET by DennisS
Dennis, you should be able to get the sheen desired straight off the gun if you use a polish with matting agent. Let's say you want a 65% sheen. You buy the formulation that's sold as 65% sheen and spray it, and you're done-- in theory.
It does mean that on a large job using multiple cans of the same product to get a consistent sheen straight off the gun means that each can has to be stirred thoroughly to get all the silica suspended in the solution. Makers of dyes, stain and polish products I've found nowadays are generally very consistent in their formulations.
If it's your preference to rub out a finish to the sheen you want with wire wool I generally suggest you apply the gloss version of the polish only and rub down from that. Something of an exception to that suggestion is where you plan to rub down very coarse grained wooods like oak and ash that you are finishing open grained. It's difficult to get into all the nooks and crannies with wire wool and you can end up with dull tops of the hills and glossy valleys if you get my drift. With these types ofopen grained timber finishes I prefer to rely on the sheen determined by the polish makers straight out of the gun or off the brush or rag.
If you apply multiple coats of a satin or matte varnish or polish you can end up with a touch of opaqueness due to the large amount of silica obscuring the light refraction. Also there is a school of thought that says that matted down polishes are slightly softer or weaker than full gloss versions of the polish, but I can't personally vouch for that claim-- It does make sense I guess, but I don't know if it's actually true.
If you're putting on let's say five coats of nitrocellulose polish (which can be built up layer upon layer safely unlike pre-catalysed lacquer) and you don't want to rub down to a particular sheen yourself I usually suggest applying four coats of clear and one coat of the desired sheen as it's this last coat that determines the sheen. Slainte. Richard Jones Furniture
Hi Richard -Thanks for the additional info.Frankly I'm not rubbing out the sprayed on lacquer finish to get a particular sheen. My problem is in spray technique. Yes, the finish "looks" fairly OK after three, four coats. But there's an ever so slight orange peel that's not up to my liking. I find that a light rubbing with the steel wool produces a 'cut' if you will on the little bit of shine that's coming off the surface thus will disquise the orange peel to oblique light and my otherwise over critical obsession for not seeing it. That, plus the fact that the objects being sprayed are solid core bedroom doors so there's a huge flat surface that's fairly easy to work on rather than inside corners such as a piece of furniture.That said, your advice to not bother with satin or semigloss material in the first place since I'm going over it with steel wool makes a lot of sense.I'm still in the process of learning the ins and outs of this DeVilbiss cup gun a painter friend gave me. It was a total mess. Someone had let some sort of chalky blue material dry and cake the thing all up. I spent two days, off and on, soaking, brushing with brass brushes and so forth getting it cleaned up. I seem to be getting good atomization and all, I have a pressure regulator for my air compressor and operate the gun at around 20PSI but learning how to adjust the air/material mixture for optimum results is an onging thing.Again, thanks for the advice ....
Dennis, what is it you're spraying three or four coats of?
If it's prec-catalysed lacquer you're building in probable coating failure. Heavy coats of pre-cat end up cracking or crazing or sometimes known as chinese writing.
Dry film thickness of pre-cat should usually be no more than 5 mils. This is achieved in two coats, three at a push.More than three coats and you're definitely taking a big risk.
Another way of removing that very slight orange peel in pre-cat is to use the polish makers 'mild' pullover solvent applied in much the same manner as french polishing with a rubber.
Pullover is not common in the US, or it certainly hadn't been heard of much when I lived there. I understand some of the polish manufacturers there are starting to offer it. Slainte.Richard Jones Furniture
Hi Richard -I'm spraying Rhoda (sp) nitro lacquer. Not pre-cat stuff. I think I need to use a thinner cut than I am. I've been to the DeVilbiss web site and looked at a number of the service bulletins (SB) about several of the HVLP guns and they all recommend thinning stock lacquer. This I hadn't done on this episode.I'm spraying my doors with them being horizontal. I have pressure from my compressor regulated down to 20PSI on the advice from the guy I got the gun from originally although many of the SB show 50PSI as max pressure at the input to the gun as optimal for proper atomization. Secondarily, I broke the gun completely down today for cleaning and inspection and I found that the 'needle' if that's what it's called, feels rough to my fingernail. Meaning I suspect that it and the cone affair that it mates to should probably be replaced.It's a combination of errors - reparing parts of the gun, fine tuning the air/material mixture and practice using it once those have been done. By now you're probably realizing that I'm a total spray newbie!But I certainly appreciate your advice.Cead Mille Failte(OK, so I learned this while in Ireland last August and I don't know how to say 'thank you' only welcome, and it's Irish gaelic but ... it's the thought that counts!)
Ah... Rodda nitro lacquer? Is that the Mar-Resist line? Rodda means that you're somewhere around me because they are a regional manufactorer. I work in Portland. Not with Rodda any more. But, I used to use a lot of Rodda lacquer.
I agree with Richard about the need to bump up your pressure on that gun. DeVilbiss's can be difficult to dial in. But, in my experience, once a good DeVilbiss is dialed in it'll perform with the best of the best. I spray all of my lacquer and conversion varnish thru a JGA 510 conventional gun and I absolutely love it.
I didn't catch whether you're using a siphon-feed or a pressure-feed set up. If it's a cup gun then it's likely a siphon-feed and those usually require quite a bit more pressure. Like 40 to 60 psi to pull enough material up the feed tube to spray on a good coat of lacquer.
One thing that you could do which would significantly improve your off-the-gun finish quality is to stop reducing with lacquer thinner and instead switch to a blend of MEK and PM Acetate (50/50). The thinner blends are as much designed to comply with EPA regulations as they are for performance characteristics. I've been using strictly MEK/PM Acetate for many years now and in my opinion there simply isn't any question that it's vastly superior.
If you do a search of the forum here using MEK and PM Acetate as the search criteria you'll find several old posts where I went into detail about what this blend does and why I love using it.
The only thing is where to get it. I get mine from the local Sherwin Williams Commercial Coatings facility. I think you have to have a commercial account to buy there, though. MEK is fairly easy to find elsewhere. I'm not so sure about PM Acetate, though.
Kevin -I'm in Mt. Vernon WA just up a ways from ya. Being a total newbie in this lacquer spray business I assumed, perhaps erroneously that lacquer is lacquer is ..... Perhaps this is not the case??I think I replied to Jamie about my 'spray session' today. In that I bumped up the pressure to a skoosh over 40psi and got plenty of material through the gun. That's with about 20' of 1/4" hose between the regulator and the gun so it's probably less than that at the tip. None the less ....Much better results! MEK! That sounds pretty nasty. As it is, with the pressure on this gun cranked to where I'm finally getting some material out the tip, the shop gets quite literally filled with overspray. The compressor's located outdoors, no shop equipment is operated until the fumes are well vented (no lingering detectable odor, and so forth. But I'm really concerned with all the fumes that linger. I don't know much about MEK but my perception is that it has a lower flash point than lacquer thinner. Not so?This thread is getting pretty fragmented but, the next question is in regards to spray pattern.On a well tuned and adjusted spray gun, let's say conventional since that's what I've evidently got here, (1) is this much overspray normal and (2) how big/wide should I expect the spray pattern to be if/when the air/material mix is correct?The overspray issue is described above. The pattern I'm getting with the gun about 6" from the surface is only perhaps 3" wide and for the most part round rather than fan shaped. I've soaked the spray head components in lacquer thinner overnight, carefully with non metalic probes tried to ensure that the holes in the air cap are not obstructed. With all this effort the spray pattern still seems to be less a 'fan' shape and more a circle. And not a very big one at that.Thanks for your ensight, Kevin.Oh - this is, as you suspected a cup/siphon gun setup.
Well, it's hard to guage the level of overspray mist just from a description. But, of necessity any siphon-feed is going to generate a lot more overspray than any other spray set-up known to mankind. If you could get a pressure cup to hook your gun up to I think you'd be surprised at how much less overspray there would be as well as how much lower pressure is needed to lay out a nice wet spray pattern.
Lacquer thinner is a blend of solvents. It used to be that MEK was a primary component because MEK is a primary solvent for nitrocellulose resin. Now days Acetone is used a lot more because it's an EPA-compliant solvent. What most people don't realize is that Acetone is a Ketone and in fact is the most similar Ketone to MEK (Methyl Ethyl Ketone). I am not at work and can't check any of my reference material... but I believe that Acetone has a lower flashpoint than MEK does. As a blend lacquer thinner probably does have a higher flashpoint than MEK. But, I never use MEK alone. I always mix it with PM Acetate and I would hazzard a guess that my blend is reasonably close to a top quality lacquer thinner in terms of flash point.
Good quality lacquer thinner is important here. Being a blend of solvents, not all lacquer thinners are equal. Sherwin Williams sells about half a dozen different blends, each suited to a different material or environment. In general, though, a cheap thinner isn't going to perform nearly as well as a more expensive thinner. What I would never, ever do is buy a can of "lacquer thinner" off the shelf at a hardware store and expect that it'll behave in lacquer the same as whatever thinner the manufactorer recommends be used.
About the width of your spraygun's fan... Assuming that the aircap isn't defective, and assuming that your air adjustment valve is working properly (ie, isn't partially blocked... which is rare), the usual suspect when you can't get a wide enough fan is the baffle which is found directly behind the fluid nozzle. It's what takes the air sent in via the air valve and redistributes it to the various parts of the aircap which then sends it thru the airhorns to atomize and shape your sprayfan. 9 times out of 10 if you are unable to get a wide fan that baffle needs to be replaced.
Kevin -You've all but convinced me to get a new setup. The local Sherwin Willams store in Mt. Vernon is a source for both DeVilbiss and Binks equipment. I'm headed there today to checkout the cost to get the one I have rebuilt and compare that to the price of a new one. Methinks a new one is the way to go.Thanks for all your advice.The overspray situation is beyond description anyway. Suffice it to say, when I finished spraying yesterday, walked outside the door of the shop, removed my repirator and looked back in I realised I had been standing in a cloud of explosive vapors. Scared the bejeezus out of me!Needless to say I'm also looking at safe ventilation systems as well.
Dennis, even if you decide to switch to an HVLP gun you'll be amazed at the cloud of overspray floating in the air if you don't use it with a decent extraction method of some sort. It may be that there's less vaporous stuff floating about, but you'd be hard pressed to tell the difference in an unvented workshop. Slainte.Richard Jones Furniture
"...you'd be hard pressed to tell the difference in an unvented workshop...."Bummer. This is not what I was wanting to hear! (grin). My 'extraction' system consists of opening the 8' slider at one end of the shop and a ragular man door at the other. An ordinary room floor fan is up wind of where I'm spraying but obviously isn't doing much good and offering plenty of ignition source for the haze of volitiles floating in the air. My spray operations are currently on hold until I obviate this situation!!I've got the guy (Sherwin Williams service center) looking into the cost of replacement parts for my 'antique'. The only HVLP gun he has in stock is a "CAPspray" (brand name) which I've not heard of for which he sells in excess of $US350. I guess I should spend the $350 on an exhaust/extraction system and be done with it.Decisions, decisions.
Richard is right about that. There would be less, but you'd probably be hard pressed to know it visually.
I'd be willing to bet that an AccuSpray pressure cup gun would yield a somewhat noticably less dense cloud of vapor. But, they're expensive and you'd still have a cloud even then.
Back to me thing with MEK... I work with a guy who was doing his own cabinets in his house... part of a remodel he was in the middle of. He was spraying the lacquer in his garage and was having a problem with rough overspray because he didn't have any ventilation and the cloud of lacquer mist was settling back onto the cabinets he'd just sprayed. I told him to stop using lacquer thinner and instead use the MEK/PM Acetate mixture. He was amazed. He still had a cloud but the overspray was noticably less pronounced. The MEK is the main culprit there. The chemistry is somewhat complex (to me) and I only slightly understand why MEK works the way it does. But, what I do know and understand is that it changes the surface tension of the lacquer particals, causing them to flatten out significantly better. Which of course means that orange peel and other forms of overspray/underspray are noticably reduced or even nearly completely negated. They're still there. But, you don't notice it because the lacquer flattens out so well that you can't see or feel it.
Kevin -I'll definitely try the MEK on my next spray project. For now, the bedroom door and frame are all but finished - I managed to get enough material on each and at an acceptable degree of 'level' that I can now tackle the final finish with 320 sanding and rubbing out with the 4-0 steel wool. This is just kinduva fetish I have on these door finishes is all. At some point when/if I ever get done with this house remodel I'll have time to think about doing some "fine woodworking". Then I'll really want to perfect my spray technique.By the way, I'm waiting for a return phone call from Bowlin Int. for confirmation on the price of one of their 20" explosion proof direct drive axial exhaust fans. This will go in one of the clerestory windows in my shop. The D2033X fan is rated at 4120cfm at 1/8" static pressure. At this rating it should evacuate the entire volume of my shop in about an hour and a half. This is good news since even with a 3HP cyclone dust collector system located exterior and ducted inside, there's still a lot of fine particulate matter floating around after doing much milling.Fortunately my wife came out to the shop yesterday to tell me something, looked in the door and decided better to wait until I crawled out from beneath the cloud. Discussing the potential cost of installing this exhaust fan, it got little argument!
A word of caution on using MEK. I personally never use it alone. I always mix it with a retarder.
FWIW... One idea for a cheaper exhaust system would be to push the air thru rather than suck it out. When you're sucking it out then obviously the motor is exposed to potentially explosive vapors. But, pushing it thru means that the motor is either not exposed or is exposed to significantly less fumes. Of course pushing is a quite a bit less effective means of evacuating the clouds of overspray. And it certainly wouldn't be my first choice. But... if it works and is cheaper then I'd probably be tempted to at least try it. I've never tried it, mind you. Just trying to think of cheap options that might get you by for now.
Good luck with the remodel.
Kevin -Just a follow up on the exhaust business -The company I contacted is currently at a trade show in Vegas. The sales rep I spoke with was actually on the floor there at the time we talked. They're offering a 20% discount, or at least I presume that's why he offered it on the purchase of their pre-assembled axial direct drive fans. I managed to get a 20" 4180CFM direct drive explosion proof unit with shipping for less than the list price of their 16" 2990CFM model. Either also come with a variable speed controller but it reduces the CFM rating to 3930CFM max. If I were to design a spray booth/room from scratch and had the luxury of the space to do so, I would opt for a positive pressure system rather than a negative exhast. The reason being it's a lot easier to filter the incoming air from dust, etc., than trying to control the intrusion of such things if the space is under negative pressure. If you're interested, the exhaust fan unit, motor, frame and plastic vaned fan blades was $US647.00 total to my doorstep UPS. The list price of the 16" model is $US658.00 sitting on their shelf. If I were to spend the time and energy to put something together from pieces, scrounged parts, etc., I think I'd be far in excess of that so it seemed pretty reasonable in my situation.I won't be doing any more spraying until I get the fan installed and get this last door hung. Along with quite a bit of drywall work, so on and so forth.No, I'm not bored (grin)
Yeah, it sounds like you've definitely got your hands full at the moment.
I don't know how much research you've done on spraybooth design, but if you're still looking for ideas I would recommend buying a copy of Jeff Jewitt's book Great Wood Finishes. Not only does it have tons of great, very easy to understand info on a variety of ways to prep and finish wood like the pros, but it also contains a section on how to make a portable (it folds up for easy storage) spray booth. Or... you could just look for it in your local library of book store and take a gander at what he has to say... drawings and pictures are included. Pages 24 thru 27. He uses an explosion proof motor so I think what you've already purchased would fit beautifully into Jeff's design scheme.
I don't have a garage or shed. So, while I'd love to have a spray booth at home, it's really not a practical option for me. Plus, I paint for a living and my employer has a 40' wide double-spraybooth that exceeds anything I'd be able to construct anyway.
Edited 11/1/2005 1:59 pm ET by Kevin
Hi, Kevin -Yes, I've visited Jeff's web site just to browse a bit. And yes, I think getting a copy of his book is in order. It's gotten nothing but positive comments. I'm particularly interested in his ideas on the break down spray booth.
Oh, by the way, Richard ....I've gotten the desired finish on these doors just today by sanding the nitro-C lacquer with 220, 320, rubbing out with 4/0 steel wool and carnuba wax. Quite a nice fairly level finish that's a joy to touch. For nothing more than a bedroom door, it's impressing most of those who drop by to view progress on my 'retirement project'.
The main thing Dennis is that you seem to be going in the right general direction and getting reasonable to good results. I suspect you might need to increase the input air pressure as I'm pretty sure from what you said that you've got a conventional high pressure gun, and thinning the material can help with atomisation, but it's not always necessary.
You can certainly thin a lot if you just want to get on a sealing 'spit' coat which is handy for things like open pored timbers where you want to prevent bubbles forming as air in the pores bubbles up a heavy slower drying full strength first coat. Spit coats can be handy for controlling blotching on blotch prone woods when they are dyed, and spit coats can reduce dye uptake in general in non-blotch prone woods or end grain to get a more even colour.
Conversion HVLP guns, if you're thinking of buying one, will reduce the amount of overspray and increase the amount of polish that goes on the target thus reducing waste. Most of the conversion HVLP guns I've used need somewhere either side of about 20 lbs air pressure at the input, whilst most of the conventional high pressure guns tended to require in the region of 40 lbs+. Slainte.Richard Jones Furniture
Richard -This makes a lot of sense, that this gun may be a conventional high pressure gun rather than HVLP.I've been experimenting with the pressures at the regulator to explore various combinations. I was instructed that with this gun, 20PSI was the max pressure at which it should be used. Browsing around on the DeVilbiss web site I see the MBC-510, the model I have, is listed in the group of 'conventional' spray guns. Not too surprisingly, I find that as much as 40PSI provides a good deal better atomization than 20 delivering plenty of material to the surface. So .....You've brightened my day once again! Now to see if all the replacement parts and tune-up kit are worth it vs the purchase of a decent HVLP setup. Of course, no post regarding potential purchase of a spray gun would complete without asking what you think about Binks equipment. (grin)Thanks again.
Dennis, Binks Bullows sparay guns are up there in the top quality group along with DeVilbiss. From Europe the Italian Asturo are a good name. There are others but the names aren't tripping off my tongue at the moment.
A couple of things to note in your settings. Firstly, if you're setting say 40 lbs pressure at your wall outlet and you have 20 ft of hose then only about 35 lbs pressure is getting to the inlet point of your gun. I'm not sure I've got the correct figure but I think you typically lose about 5 lbs pressure per 10 foot length of hose. This, if I recall rightly, depends a bit on the internal diameter of the hose, 1/4" dia losing more pressure per foot than 3/8" or 1/2" dia hose. Someone will hopefully have the correct figures to hand to let us know and will post.
I like to have a pressure gauge in the airline as it enters the gun as this is as accurate as it can get, assuming the gauge is accurate of course. If you get one of these it's the reading you get when the trigger is depressed that matters, although you can approximately estimate inlet pressure from the wall gauge if you know the hose length and pressure loss per foot.
Matching the needle and nozzle matters too. A big needle and large nozzle requires more air to atomise the fluid properly. For spraying most nitro-cellulose type lacquers, including pre-cat and acid-cat I mostly use a 1.1 mm to 1.4 mm matched sets. This is easy to coordinate with the European guns because the dimensions are marked on the parts. I found it harder to do this with DeVilbiss and other American guns because coded numbers had to be matched and as I recall there was no obvious correlation between the number codes and size. You have to refer to a chart supplied by the gun maker, which is fiddly and a pain in the pants, especially for me as thousand'ths of an inch don't mean much, and I have to convert to millimetres to get an idea of what size is being described, ha, ha. Slainte.Richard Jones Furniture
Thank you, Richard, for not only providing some knowledge about lacquer formulation (of which I'm ignorant) and also for giving me a better vocabulary when responding to "How much ice cream do you want?" A fair wodge sounds just about right!
(my apologies Dennis, couldn't resist)forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
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