Official Luthiers Forum!

I don`t think this subject has really been touched upon directly, unless I somehow missed it, and I`m here every day, so here we go...
Finishing my work could be a success or demise at this point in time.
I would like to thank all those who reply to the questions and issues in this part of the process.
I`ve been reading and taking notes, even geared up with dedicated spraying rigs, 2 total, with another one as yet to be determined.
The research I`ve accumulated has all but melted into the background of my mind, and I need to get things into gear, albeit slow.

Man, I like our "speelchecker" (elbow at ya Lance)! KUDOS!

How much time and cash does it take to finally decide when it`s either do or die when it comes to deciding on which finish/method/schedule?
Now I`m not talking about throughout our finishing careers, but rather the one at a time situations.
I have yet to settle on any single one.
If we test on scrap:
If it works without measuring and just giving it a wild guess, and then again another time it doesn`t, you have to back up just a bit and reconsider. I AM A FIRM BELIEVER THAT NOTHING, NOTHING IS A CONSTANT.
Does the shelf life on unused, yet opened products diminish significantly (over time, of course)?
Will a special mix of, for example, toned lacquer stay viable on the shelf while waiting on results on different test panels?
I do in fact realize that there are many, many variables involved.
The basic rule of thumb in my mind says to give each sample 30 days before final addressing.
Will stains and dyes stay suspended long enough to use again before we waste it away into the cat litter for later disposal?
I`m just trying to get a real grasp on the cost and time and benefits/disadvantages.
Coe Franklin

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,

this is a really tough question to answer, I guess it depends on what resources you have, what equipment you have and how much time you want to spend. I use lacquer, the main reason is I have lots of experience using it in my career as a cabinet maker. I have access to a pro spray booth with explosion proof fans and a drying room. If I were finishing at home I'd likely choose another kind of finish, french polish, varnish Idk, but I didn't have to search very far to find a finish that I was comfortable working with. For me it was simply a matter of buying the material and picking up a gun.

I am just starting to use some water based lacquers at work and so far I really like them, much better than the stuff I've used in the past but I have limited experience with them and can't attest to polishing them or cure times or really anything. I can say the dry time and lay out is improved compared to what we've used in the past, and things seem more consistent sheen wise.

I'd say this question is too complicated to easily answer, what are you most comfortable with? What have you had the most consistency with, and what finish gives you the look you want? I've found that most finishing issues come from user error, poor prep, not being clean in your environment or with your equipment, not understanding how to set up your gun, applying too little or too much finish at a time, and not taking the time to understand the qualities of the finish being used. There are of course environmental factors to consider but my thinking is, if you don't understand the way the finish is supposed to perform in an ideal situation you cannot recognize when an environmental condition is contributing to a failure. Which brings me to your next question...



I don't have a ton of experience finishing guitars but I've finished hundreds of cabinets and doors at my shop. Recently I took over the finishing department and there were a lot of things that needed to be corrected. One of the big things was trying to increase the consistency of our finishes. My boss was very much about doing things without measuring, he figured you can just do everything by feel. He was okay with the guys who were running things before doing the same, and guess what? Totally inconsistent results sometimes within the same job. The key is controlling as many factors as you can which will result in a successful finish. These include having your equipment clean. This is not just the spray equipment but mixing vessels, stir sticks, using filters, keeping things above and below your workspace as dust free as possible and keeping yourself as dust free as possible. Using the proper thinner or reducer if you are using those, stirring the finish properly before use, (which isn't as much a factor with pure gloss finishes as with satins and semi's). If you are mixing a post catalyzed finish using a digital scale and doing the proper math is a must. Doing such finishes by eye is an invitation for disaster. Following a proper finishing schedule includes knowing the proper cure times before re-coat and following these. It is always, ALWAYS easier to finish things properly the first time than it is to try and scrape, sand, strip your way back to a pristine enough state to begin the finishing again or to come up with a fix. If you are prepping things properly, pore filling, sanding, sealing and spraying the finish properly which may include getting a wet mil thickness gauge until you get real comfortable with your finish, (and even then it's a very helpful tool), then theoretically the only other factors should be environmental and compatibility issues. Compatibility issues are another things that should be tested for and many of these can be ferreted out by reading up on the materials before you even get to that step. Environmental factors are at this point the biggest difficulty for me, my formula's change as the weather changes because both temperature and humidity play a role in how our finish is working. If things are drying too fast from warm weather I drop the level of thinner in my lacquer or switch to butyl acetate which dries slower. This helps us avoid striping in our finish and blushing as well. We thin our material because we are spraying both open and closed wood grains and full thickness material will result in pinholing on open grained wood. It shouldn't be an issue on a pore filled guitar and I like to shoot straight lacquer on mine. That's just an example of an environmental factor.

My opinion again is do everything you can to control what you can control. Take notes about what steps you took to achieve a finish and what you like and don't like about that finish. Writing this stuff down not only gives you a record of your successes it also helps you recognize patterns in what works and what doesn't. Eliminate the guess work and you'll solve the mysteries of finishing. Like I said before if you understand the way a finish is supposed to perform under ideal conditions that will give you a starting point to understanding why they fail in less than ideal conditions, which will help you make the adjustments necessary to stop the failure. I feel good knowing that as long as I follow my formula's I should be fairly close to being successful and the adjustments I need to make should be small. Just remember what works in the winter won't work in the summer necessarily, but what works on Monday should work on Tuesday.



the shelf life of any open product is shorter than an unopened one, but varies greatly from one product to another. I've had oils harden up in a matter of weeks, I've had solvent based lacquers last for years. Water based stuff is tricky, one of the big problems I've noticed with that stuff is before the finish goes bad the can or the lid will rust, this is getting better since more cans are being made out of pure plastic but this is a problem I've seen with products within even the last couple years. The best thing to do to ensure a long shelf life is to keep it in as small a vessel as possible with as tight a seal as possible. When I took over the spray dept. a lot of stuff was being kept in plastic mixing buckets with lids on them. These were in various states of accelerated failure from hardening, drop out (precipitation which you will see in dye stains where the color particles cling together and settle out of the mix, unable to be dissolved again.) My solution was easy, I went to the paint store and started buying empty quart and gallon, metal paint cans which I labelled with the contents and a white tag that I could smear some of the color onto to quickly identify in our storage cabinet. Keeping the lids tight will greatly extend the life of an opened product. As to how long things should last, your tinted lacquer should last as long as an untinted lacquer as far as I know. I've not noticed any difference in my experience, but as to how long that lacquer should last consult the PDS and ask the supplier if they can tell you how old it is. I live in a fairly big city so as long as I go to a reputable supplier the product is getting turned over pretty fast. If you're buying something from the hardware store, who knows how long it's been sitting on the shelf.

Thirty days? You should be fine with most things



Stains and dyes should stay suspended for a very long time, this of course depends somewhat on how they are made in the first place. The deciding factor for a dye will be the solvent that's used, and how tightly it's kept sealed. I mainly use dyes for spray stains and I like to use lacquer thinner as my solvent. I have had two different types of lacquer thinners behave totally differently in terms of making toners. Some lacquer thinners contain partly recycled lacquer thinner and these can cause headaches for finishing. I am fine with using these to clean up with, but I don't like them for making stains, toners or thinning finish. The reason is seasonally, they may contain differing amounts of water which can wreak havoc on your formulations. Water in a finish can cause blushing, whiting, bubbling. In toners I've had such thinners work fine with aniline dyes in one batch, and the next batch of thinner doesn't act the same. It's too big a chance for me to take, and so I go with virgin thinner on that stuff. I've also had one type of LT cause almost immediate drop out of yellow dye in a blend, and more slowly brown dye. This was remedied by adding acetone but since it evaporates quickly the fix was temporary. If you are having dropout issues don't even mess around, switch your thinner. I like lacquer thinner for mine btw, because I spray it onto lacquer and it gives me an immediate grab. Alcohol will grab lacquer too but it doesn't do it fast enough for me, and my impatience with it easily leads to runs. I've never had a problem mixing dyes with water but storage becomes an issue if you're using metal cans. If you're worried about shelf life with dyes you can always mix as you need it, and the aforementioned digital scale will help quite a bit for that. I like to mix a small amount first until I get the exact color I want, and then for a spray stain I'll dilute by adding twice as much thinner as I had in there in the first place. If I were going for a wiping type stain then simply increase the amounts of the dye concentrate and thinner accordingly. Keeping notes of your toners is especially helpful when you start blending colors, I'm not talking lab scales here either. Harbor freight has some cheapo scales that go to tenths of a gram which should get you close. Once you're in the ballpark a drop here or a drop there is usually enough to get things right.

As far as stains go, the parts that make up a stain are the pigment, the vehicle (a lot of times this is mineral spirits), the binder (some kind of oil) and in some cases a drying agent such as Japan drier. The thing that goes bad first is the binder. We make a lot of our own stains from scratch and we use a non-linseed, penetrating oil. It has a shelf life of 24 months I believe. This is its shelf life in its pure state, I think that our stains actually outlast the pure penetrating oil. You should be able to tell whether a stain has gone off when you start to stir it. If there are sheets of gelatin like material in it it's toast, no amount of stirring will bring it back. Also if the pigment has dropped out and just wants to stick to itself instead of dispersing that's a problem too. That said, I've had some commercial stains last for years and years. I probably have some stain from 7 or 8 years ago, and it still seems viable. Again I think the big issue is proper storage. It really pays to keep stuff in nice metal cans, put a board on top of it and whack it with a mallet a few times to make sure it's good and tight. Really an ounce of prevention to prevent a lot of waste down the road.

What he said I guess.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

How much do you got? I have been finishing wood for almost 30 years and I am constantly testing out newer products and application schedules. The products change with increasing regularity these days and testing is the only way to stay on top of it. I never consider the process to be perfect, there is always room for improvement somewhere, be it in the actual coating, the chemistry or the application.



That depends on what type of "lacquer" you are referring too. Assuming nitro, yes, they should be fine. I have had colored acrylic lacquers that were still viable after 15 years. Nitro generally has a very long shelf life, in fact even if it dries out in the can it could be reconstituted with the addition of solvents. This is the same feature that allows repairs to "melt" into the old surface.



Depends on what you are trying to gain by running the sample. If it is for color/tone then the coating does not really need to cure fully. If you wish to test adhesion or durability then a full cure would be recommended and that will vary by coating type and manufacturer so it would be best to inquire of the tech dept. to find out how long that should be. If it is for process assessment you may not even need to finish the sample to find out what you wanted to know.



Again I have had stains that were still completely viable after a decade or more. A lot of this may depend on the products you choose. I mostly use industrial products that are not available readily to the public. I can not say exactly what other coatings may or may not do. Some of this will depend on your storage of unused materials. Tightly sealed in appropriate sized containers in a temperature stable environment will improve shelf life considerably.

Finishing wood is a whole other discipline completely separate and different than making things of wood. It is a process, it is chemistry, it is tools and technique, safety considerations etc. etc. For those who don't want to deal with all this there are those like myself who will do it for you.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Best sick with your beliefs then.




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Audiences and dispensations on Thursdays ~ by appointment only.


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Thanks a lot for the replies, guys.
You are affirming my thoughts about this matter, with a few tidbits that I really didn`t consider.
Ain`t but one thing to do, and that`s to get spraying and get a feel and plan going on.
Coe Franklin

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,

Hehe...I was also going to say something smart alecky to that because the fact is.....every chemical you buy is pretty darn constant. How a certain chemical interacts with other chemicals is also pretty darn constant. The only variables are temperature and humidity...and they are controllable too.

The problem is that you are faced with a quest that can be achieved a couple of million ways and without clear directions and a methodology, such a quest can fail due to a lack of focus or a failure to remember the lessons you've learned.

1. Write it down. When you mix something and you are wondering how long it may last, write what it is and when you mixed it on a piece of masking tape and put it on the container.

2. Write it down. When you test a finishing schedule on a piece of scrap, make that piece of scrap a standard size, say 8" x 3" x .2". All throughout the test you can write the ENTIRE DETAILED schedule out on the back of the test piece and then file it when you're done. Include the sanding grits for the prep. The whole thing. Success or failure...you'll have a visual reference and the exact schedule that produced it. Your scrap test library might come to be one of the most important references you have. Don't let your experience "melt into the background of your mind". Rather, have it sit there on shelf...as a permanent reference.

3. When an experiment shows some promise. Develop a WRITTEN plan and follow it verbatim on one or two more test panels before approaching an actual guitar. Finishing a guitar has its own unique set of problems. KNOW that your finishing schedule works consistently on test panels before you add the variables of the guitar into the problem.

4. Don't be afraid to experiment but do so AFTER you follow a manufacturer's specific schedule from raw wood to polished finish. When a company (or dealer of a certain brand) actually has a recommendation for a polishing schedule for their systems, it's a strong indication they have comprehensive experience worth following. Although the chemical itself may be consistent, the companies that make these systems range from expert to novice in how they are used.

5. Finishing is far and away the hardest part of making guitars for me. And although still anecdotal, after nearly 20 years of making another product I can attest to the fact that obtaining a world class finish is the hardest part of "making things". A methodical approach, copious, clearly written notes, and a strict adherence to a finishing plan will accomplish the goal in the shortest amount of time and at the least expense.

Note that the test panels in the pics vary a bit in size and there are other odd sized pieces next to them. This shelf contains only a part of my finishing experiments. When considering the number of standardized pieces it's worth noting that they represent maybe 1/3rd of my overall experiments. I didn't really follow my own sermon, as written above, but came to the methodology of using standardized panels after flailing away for some time with odd sized pieces. I used to number the specimens and make computer notes but I found that writing the whole thing out on the back served me better.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Stuart, That's a great record keeping system!

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Jim Watts
http://jameswattsguitars.com

Thanks, Jim...I got downtown with it.

My guitars are hard to sand. I didn't have to strip and sand all that many of them way back down to bare wood before I decided to break the problem down into smaller chunks.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Stuart, that's similar to what I've started doing though I'm not writing everything on the backs of my samples. I keep a 5x8 finished sample of 3/4" with a code for job name or contractor, wood type and general color on the edge. Then they go into a bookcase and I can quickly pull out multiple samples of maple or walnut to show customers a spectrum, or a color and how it looks on various woods.

Then all of my notes go into a file with manufacturers data and supplier info so if we need to order more I can just give them the order number. It's kind of tedious, but way less than trying to guess two years down the road on how to do a finish, especially since our finishes often include wiping stain AND a toner. Total pita to redo those from scratch blind.

Stuart, thank you very much for your reply without the "smart-aleck" jab.
I was too worried about saving the pieces that I was wondering what to do with might have some value later in time for another project.
They do now!
I never thought of something like that, thinking that writing it all down for later reference would suffice. After four legal pads covering different subjects, finding the pad isn`t always easy, and which pad did I write it down in?
The computer sent me down another leg of the rabbit hole. Takes up too much time that could be spent in a more wise manner.
Your method is all too simple!
A lot less hassle on that part.
Now, let`s see, here. I have one half-pencil. I suppose I should write it down twice, no?
Coe Franklin

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,

Haha...you're welcome but I almost did.

Besides, Padma's just a teddy bear...you pull a string on him and he either makes a wonderful artifact, or gives sage advice, or he says something very silly.

You'll probably defeat yourself if you truly embrace what you wrote....that nothing is constant. Constant is your goal. All your chemicals actually ARE constant. The trick to finishing is to learn how they work and to revere consistency as fundamental to the art.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic