finish

[mandolinplucker]

I have done nitorcellulose laquer so I know that one. There is also spirit varnish, varnish, and shellac. Then tung oil and true oil fits in there somewhere. I am almost ready to finish a ukelele and I am working on two mandos. I would like to try something different on the uke so that I will have more choices that I have some experience with when I start finishing the next mando. Ain't this stuff fun??

[mandolinplucker]

PS. I don't need a lot of directions for application. I'm sure that I can find most of that in the search archives. I would like the definitions and pros and cons of each. Just thought I'd clarify the question.

[sunburst]

Well, none of the experts have tackled this one, so I'll take a stab at it, and anything I get wrong will probably get corrected, and I'll learn something in the process. (Sometimes it's easier to learn something by giving the wrong answer than by asking the right question. )

Just about any clear finish coating can be loosely lumped under "varnish", including lacquer, but the usual kinds of varnish are spirit varnishes and oil varnishes.

Spirit varnish is shellac dissolved in alcohol (spirit). The simplest would be just that; shellac dissolved in alcohol, but usually oils and/or resins are added. There can be other ingredients, like ground crystaline minerals, and on and on.

Oil varnishes are resins mixed with drying oils. Drying oils are oils that polymerize, actually, rather than dry. Polymerization is a process where small molecules link up to form big chain molecules, and in this case, the oils change from liquid to solid in the process. Common drying oils are boiled lindseed and tung oils.
The resins can be natural resins or synthetic resins. Some natural resins are; amber, shellac, copal, sandarac, etc..
Some synthetic resins are; phenolic, alkyd, polyurathane, polyester, etc..
The ratio of oil to resin is one of the ways to control the properties of the liquid varnish and the characteristics of the cured film. More resin and less oil is refered to as a "short oil varnish", and is harder, easier to buff and more likely to cold check. It is best for furniture and indoor items where extremes of heat and humidity aren't normally encountered.
More oil and less resin is refered to as a "long oil varnish", and isn't as hard, but will withstand more wood movement, and is the type of varnish that can be used outside. Spar varnishes are long oil varnishes with UV stabilizers and other ingredients added.
Of coarse, there are varnishes intermediate between long and short oil varnishes too.

Tung oil and Tru-oil are usually oil varnishes. At least most of those products sold comercially as tung oil for finishing wood are. Pure tung oil will polymerize, but usually "driers" and resins are added to the comercial products, making them varnishes.
I think Tru-oil is boiled lindseed oil with driers and resins, but I could be experiencing faulty memory again, and it might be tung oil. It's actually a varnish too.

Now days, there are many "modern" finishes that are catalyzed. They are conversion varnishes and the like. They aren't much like the "regular" varnishes (oil or spirit) and I don't know much about them.

This is just the basic stuff, here. There are enough books on wood finishes to fill a huge book shelf. If you want to read one book that will give you a pretty good working knowledge of wood finishes, I recommend Understanding Wood Finishing by Bob Flexner.

[Rick Turner]

John, you're on the money as far as you went. I use a lot of "modern" finishes in my shop...polyurethanes and polyesters. I'm writing a pretty comprehensive article for "Guitar Maker Magazine" on "Modern Finishes for the Small Shop." I also directly stain bare wood for a lot of colors and 'bursts, then lock in the color with tung oil, and then shoot the modern finishes over that. The result is a very Loar era-like look, but with the incredible protection and adhesion of modern catalyzed products. It's very much a hybrid of old and new tech.

[jim simpson]

Would staining a top black then clear coating be a good way to do a black top?

[sunburst]

Yep.
You can stain, or paint it black, then clear over.

[Antlurz]

Loved that post, John.

Thanks. A fun and informative read. Till just now, I had never considered the possibility of actually using linseed oil on a musical instrument.

Ron

[Chris Baird]

It would be a fine thing to do away with the term "varnish". The word alone means almost nothing and leads to much confusion. It is best to just refer to your finish material by it's name. They all have names which specifically identify them beyond "varnish". "Varnish" is only useful to salesmen. We builders should be more specific and abandon trying to corral various finishes under some ambiguous umbrella term. Once a classification becomes too broad it looses its praticallity.

[Rick Turner]

Right on, Chris. Also, lacquer doesn't mean much anymore in terms of chemistry. Oil + resin = varnish the resins can be "natural" or they can be polyurethane, phenolic, or whatever. It's varnish...telling you very little.

[8ch(pl)]

There are 3 principal manners in which a finsh can harden or dry. They are Polymerization, Oxidization and Solvent Evaporation.

Polymerization is a term normally normally restricted to synthetic finishess. Polyurethanes and epoxies generally use two chemical resins which react together genrating some heat and the resulting chemical reaction forms a hard finish surface.

This is just a basic overview. I was an Aircraft Refinisher in the Canadian Forces for about 20 of the 25 years that I seved.

There are also one part polyurethanes that use two different methods, UV Polyurethanes are hardened by ultraviolet light, Linear Polyurethanes by reacting with the Humidity in the surrounding air.

Two part Polyurethanes are dangerous to the user's health in that they produce Di-Isocyanates. This is the Chemical that killed about 3,000 people in the spill at the Union Carbide Plant in Bhopal, India. It's use in the Aircraft and Automotive Industry has cause a lot of health problems probably leading to several deaths. This is the most durable paint product available. It is my understanding that the mixing of the two components generates the most Isocyantes, however, the danger to humans continues throughout the application and curing of the product. Industry Safety Standards in many Jurisdictions require wearing Air Supplied Respirators and stringent policing of the work area to prevent the inadvertant exposure to Isocyanates.

Two part Polyurethane foam such as that used in boat flotation and in the packaging industry are equally dangerous. There is less Isocyanates generated by UV and Linear paint systems, as well as the aerosol foams used around the home. These are safely used in adequate ventilation.

Varnishes and enamels dry by Oxidization. Sunburst is otherwise correct in his discription of the drying process. The components in the paint react to Oxygen in the atmosphere. The spirits in the finish act to help evenly distribute an even thin coat. After they evaporate the Oxidization Process takes over and continues until the finish hardens to the touch. It continues to cure until it reaches it's maximum hardness. This may take several weeks.

Lacquer finishes use Solvent Evaporation to harden. All fiishes require some solvents to carry the finish product. with lacquers however, the finish is hard as soon as all the solvents evaporate. Lacquer finishes can often be applied and fully hardened in a matter of minutes full curing in as little as an hour. Because of this spray application is normally used.

[Dennis Russell]

Hello Glen: I read your post several times on the dangers of Iso cyanates and its use in Polyurethane. I was An aviation structural Mechanis in the U.S. Navy for twenty two years. One of our jobs was Corrosion control, that means stopping the corrosion on the aluminum and steel surfaces, but it also meant we had to treat the surfaces and repaint or do touch up work. We first used lacquers in a small touch up applicator but later started using two part epoxy. WE were told to use in caution it could be toxic, no one in my squadron had any knowledge of dangers of epoxy. We were told to use a simple cloth dust mask only and later use some neckerchefs wrapped around our faces.
in Later years when I went to the two week course in North island San Diego on paint removal, corrosion control and treatment and re-application of coatings, (They ere using Polyurethane) . It was stressed that this coating was not to be used to refinish aircraft surfaces in a local command level. It was to be used in a contoilled facility with special clothing and breathing apparatus. When I got back to my command they Poo,d poo,d at this and told us to use it anyways . I today have Asthma caused by use of this stuf, I bought my own protective devices because the military command at that time ignored warnings of this stuff.
I also have other respiratory ailments, but I have managed to keep it in check. I repair instruments and do some building of mandolins and guitars, I use Lacquer, but make sure I dress appropriately and have plenty of ventilation in my spray booth out side. I just recently started using these kits of varnish used for violins that I bought from International luthiers supply in Oklahoma, it is put on with a brush. I would like to know where I could find information to use this with a small air brush application and how to thin the mixture for application.
Dennis In Yuma Arizona

[Chris Baird]

Basically, a spirit varnish is shellac dissolved in alcohol. There can be other things added to the mixture to make for a softer or harder finish but when one talks "spirit varnish" think shellac. French polishing is a process for applying dissolved shellac and isn't a finish in and of itself.

[Smyers]

A note in Isocyanate:

I work for a company that used to make isocyanate metering pumps that were used for the manufacture of foam cusions, like that used in autos and boats. #The other more benign substance used in this process is polyol.

One of my work assiciates was involved in the sales and developement of this product. #After a few years, he developed extreme reaction to the isocyante, followed by vaqrious health problems. #Within a couple of more years, he devolped and extremely rare liver cancer and has since passed away. #He was less the 50 years old. #Suspicious to say the least. #I have been aorund the isocyante a bit myself, but realized very quickly how dangerous it is. #I ended up refusing to work with the pumps and told my boss I would rather be fired than work with it. #I can't emphasise enough how nasty the stuff is.

So I just wanted to add what Glen said. #Stay away from isocyante finished folks. #You'r not impervious to it, as my work associate found out and it's simply not worth the risk.

[Rick Turner]

Practically every autobody shop in America is shooting catalyzed (two part) polyurethanes, and some of "linear" polyurethanes that I've encountered in boat yards (Dupont products) are catalyzed and do have Isocyanates. No doubt that they are nasty...but they're a lot more common than you might want to think, too.

I have a fully regulation spray booth inspected by the Monterey Bay Air Quality Control inspectors on a yearly basis. Any of us who spray wear full Tyvek "bunny suits" with a hood, and full breathing apparatus with properly rated filters. We wear gloves. We sweat like pigs in those Tyvek suits! But I think...I hope...we're safe.

Several finishers who I know feel safer around polyester than nitro lacquer because the outgassing of freshly sprayed lacquer goes on and on and on...and the booth and finish departments stay very stinky for a very long time. With the polys...urethanes and esters...the solvents flash off within 24 hours and they are gone. You can put your nose 10" from a polyester finish the day after it's been shot on and barely smell anything other than your own breath...and that's your problem! So I think there are health issues no matter what kind of finish you use, and you should be well aware of them and act accordingly. I feel safer around my catalyzed finishes than around nitro. And as for spirit varnish, shellac, and French polish...try to use consumable alcohol...the highest proof Everclear or lab grade non-denatured stuff. Alcohol can get right through your skin, and since most people who French polish don't wear gloves because it screws up the feel of the process, that de-natured alcohol so often used is poison.

[Dave Wendler]

Thanks to all for their contributions on this subject. We should ALL be aware of the dangers associated with finishing.

I've been using waterbornes for over five years, in addition to tung oil.

Lately I've been experimenting with tung oil OVER the top of the waterborne polyurethane. Three or four coats of tung oil, buffed with 0000 steel wool, then buffed with hard floor wax...gives a GREAT sheen; glossier than a satin finish, and much mellower than full on gloss. Reminds of oil varnish on a hundred year old violin.

[sunburst]

I remembered waterbornes after my post above. I thought about editing in some info on waterborne/cosolvent type finishes, but I don't remember all of the admittedly limited knowledge that I had about them, so I'm leaving that to someone else who knows about them...(?)

[8ch(pl)]

John (Sunburst), I meant no rebuke to your post about hardening of varnish finishes. Actually, Oxidization is probably a form of Polymerization in the same way that Linear Polyurethanes use Humidity as a catalyst.

Dennis, I joined the Royal Canadian Navy in 1966 and worked as an aircraft mechanic on Grumman Trackers. In 1972, after the Canadian Forces Amalgamation I remustered to Aircraft Refinishing Trade, formerly it was an RCAF Trade. I retired in 91 after 25 years, so most of my previous post comes from that experience. I was Sergeant I/C of the Refinishing Section in Greenwood Nova Scotia when I finished. We flew a variation of the Lockheed P3. We did all of our touch up work with Epoxy, which used to go "Chalky" because it did not stand up well to Ultraviolet. They asked me to prepare a paper about the use of Polyurethane paint at our unit, the Aircrew were always complaining about the Blotchy look of the finish. I copied the pubs and more or less stated that our facilities could not follow the Forces' Safety Guidelines. I concluded it with the statement that Aircraft cosmetics could not take precedence over health and safety of our personnel. The Major who requested the paper put a minute on it that he was looking for "Positive Solutions, not Excuses". The suck-up Warrant Officer that I worked for told me that it was not good enough and that I would be discussing it with the Major. I responded that the only Officer I intended to talk to was the Base Surgeon. That was that, the Warrant Officer got promoted and I got out when my 25 rolled around. Politics.

I too have some bronchial problems from those days and I did my best to avoid spraying Polyurethanes. A couple of guys in my trade died from cancer. Another got sick from using the stuff in the small aircraft programm in Trenton. They stripped and sprayed a small jet every 3 weeks there. He had a lymph gland in his groin removed that was fullof Isocyanates. His skin pigment dissappeared in places so that he had patterns that were Olive and the rest almost Albino. After his illness they told us in a message that cartridge masks were no longer to be used for polyurethanes and they started to provide full face air supplied resrirators. Some years later,this same fellow was working for me in Greenwood when I wrote the papeSorry about the non mandolin content, just wanted to share this with Dennis, since we were both Sailors.

[Rick Turner]

I probably need to go to a supplied air full face mask setup. I do have excellent exhaust in my booth, so at least that's good.

As for waterborns, they were a disaster for me. I like to say that the main ingredient is wishful thinking. When Bob Taylor switches to water born finish, I'll believe its time has finally come. 'Til then, though, I like polyester a whole lot for most of what I do. Next choice is satin urethane, next would be nitro lacquer. But then I've got a production shop, and that changes things a bit.

Is the varnish that Gibson is using a long oil, short oil, or spirit varnish?

[8ch(pl)]

This post is for Rick Turner.

The obnoxious smell of lacquers is an indication of their toxic nature for sure. However it is different for Di-isocyanate producing Polyurethanes. The Canadian Forces Publications that I used stated that Isocyanates are generated in toxic concentrations long before they can be detected by smell. The stuff is cumulative, and is highly suspected as a carcinogen. I have heard both that it is and that it is not, so I do not want to say without researching. People become sensitized to Isocyanates and it becomes worse with repeated use. The painters you meantion are in my opinion under a false confidence with these products.

I believe the Health Dangers from the foams and finishes used in the Aircraft, Marine,Packaging and Automotive Industries - among other users, are one of Industy's best kept secrets.

I am sorry if I sound harsh, but I hope the stringed instrument trade doesn't join in this. Some of us need our lungs for singing. I have a great affection for all of you in the Cafe.

[Rick Turner]

Thank you, Glen.
We do keep the spray booth fan going far longer than just when we're spraying, so we do try to pull a constant flow of fresh air through the finish department. Spraying is strictly done in the booth, no more than three feet from the overspray filter traps. Instruments in early cure are right behind the spray station, so the air flowing through is carrying nasties up and out.

[Mario Proulx]

Rick, in between coats, and for the following 12 hours, I have a small ventilation fan(bathroom fan, actually...) in my booth that I use. I'll shut down the main blower after shooting, and turn the little ventilation fan on. It's not explosion-proof, but the blower pulled everything out before i switch to this one. It pulls about 75-100CFM, which is enough to keep air flowing TO the booth(and outside), and away from the rest of the shop, yet isn't pulling enough air to screw up the temperature and RH too badly(a big deal for me in winter, when it can be -40 or less....) Despite how strong polyester smells, there's no hint that I'm shooting it at all.

[Rick Turner]

Yes, thanks Mario. We plan to do exactly that. Right now we're putting in an airlock room just outside the finish department and we need to bring in outside air for makeup of the exhaust rather than pulling shop air through a bank of filters as we're doing right now. We also have a perfect room to use as a hot box, but we just haven't needed it yet. It used to be a bathroom, and so there's even a perfect vent stack there in which we could put a fan. So much time, so little to do!

[buddyellis]

Alcohol can get right through your skin, and since most people who French polish don't wear gloves because it screws up the feel of the process, that de-natured alcohol so often used is poison.

Depends. If you use everclear like alot of people seem to do, its just pure ethanol. You can also buy denatured alcohol which does not contain methanol. The alcohol I buy is denatured with isopropal, which is just plain rubbing alcohol. Wouldn't wanna drink it, but its fairly safe for contact.

I use spirit varnish because I have found, for me, working in my dining room, its the only finish that doesn't smell the world up while it's curing. Oil varnishes stink for days, lacquer is just nasty, and the various poly's just aren't an option for me -- I just don't like them. French polished spirit varnish is really not that difficult to do once you work the technique out on the first instrument or two. It is alot more time consuming than lacquer spraying though.