Jump to content
Maestronet Forums

Spirit varnish without shellac


Michel Aboudib

Recommended Posts

18 minutes ago, HoGo said:

You can get pretty deep shine with Tru-oil.

That is true. From the link I posted above, that has a recipe making tru oil ('Tru-Oil' is made from a mixture of 56% mineral paint thinners, 33% oil varnish and 11% linseed or Tung oil. The exact specification of the components are, of course, a trade secret.) , is it possible to make our tru oil (for a better quality)? 

For example: For BLO > washed linseed oil with titanium/zinc oxide white (as drier), for oil varnish > colophony turpentine mixture and mineral paint thinners?

Link to comment
Share on other sites

On 10/26/2020 at 11:23 AM, David Burgess said:

Four or five steps into that photo sequence does reveal what appears to be dirt accumulations, corresponding to "reduced-level winter grain lines'.

So far, I have reached out to the curator of the Ashmolean Museum, the curator of the National Music Museum in Vermilion, (both of which have Stradivari guitars) and Charles and Peter Beare. Next will be Andrew Dipper, who somewhat specializes in early instruments. It will be interesting to see what comes out of all that, if anything.

I spoke with Andrew Dipper yesterday. He has probably had more exposure to  a wider variety of early instrument than anyone I know, who is still alive and kicking. He was also of the opinion that the tops of lutes, guitars etc originally had a raised-summer-grain scraper finish, but that such practices may have started to change or go downhill around the time of Guadagnini.

My personal opinion is that guitar makers lost their way somewhere around that time, as well. Is there a guitar or mandolin maker who is brave enough to resurrect the “old ways” rather than their main influence being smooth factory-type finishes? That's what I would do, if I were to make an acoustic guitar.

I don't think I articulated my question very well to Charles and Peter Beare, but Peter expressed the opinion that even if the flat tops were done with a plane, they would have been tidied up with a scraper. He said that he'll look more closely for artifacts the next time he visits the Ashmolean Museum, describing the Ashmolean's guitar as being the best-preserved of the Stradivari guitars.

I've sent a link for this thread to Dipper, in case I've accidentally mischaracterized anything he said, or he has something to add or subtract.

I don't expect to hear back from the National Museum of Music any time soon, since they are temporarily closed during a building project.

Link to comment
Share on other sites

1 hour ago, David Burgess said:

He was also of the opinion that the tops of lutes, guitars etc originally had a raised-summer-grain scraper finish, but that such practices may have started to change or go downhill around the time of Guadagnini.

 Peter expressed the opinion that even if the flat tops were done with a plane, they would have been tidied up with a scraper. 

It seems a time consuming endeavor to scrape a soundboard to get a raised grain after a bridge and rosette were glued.

The answer may be found researching the neopolitan mandolin and guitar makers first and then research some of the guitar makers before Martin.

Link to comment
Share on other sites

On 10/27/2020 at 7:47 AM, Michael Darnton said:

You should know that you might have trouble with nitrocellulose directly over oil varnish. Nitro is susceptible to failing to harden in such a situation, as it can pick up the oil as a plasticizer.* This can happen if the oil isn't totally dry, or also because lacquer thinner is a solvent for oil, even when it's dried. 

*factoid: if you use a 60s hippie cloth guitar strap with plastic on the inside, don't store it with the plastic against the guitar--the plasticizer will leak into the guitar finish and leave a soft stripe up the back! Nitro LOVES plasticizers.

Yep, gotta agree.  All of the oil varnishes can't be of the same formulation store bought or homemade.  Mine was based on aged, aired spirits of turpentine with all other ingredients added to that afterwards.

I had problems getting a glass smooth finish on the conifer tops, not really a problem with side and neck wood but I knew nitro sprayed would makes things better.  Would spraying over my own dried oil work?  Let's find out - this was last winter.

First thing I did was realize I didn't want to buy another quart of lacquer thinner.  I've got enough now to load a sprayer and to clean up with when done.  I've got another problem.  The regulator on the air tank doesn't want to work now so that means the Campbell Hausfeld is out of commission.  I do have this though - a Wagner fine finish power painter.  Hmm, the spray tip housing looks similar to an airless, let's see how far I get.

So, first things first, decide how much castor oil to use.  The only info. I had on that was from an old Gibson guitar man from the old days though he didn't have the amount needed for guitar work.  Must of been a trade secret.  Ok, let's try this mustard jar from the sausage and cheese gift set for starters and fill with one ounce of 90% isopropyl.  Drop in castor oil one drop at a time and see what happens in the alc.  Hmm, let's stop at seven or eight drops.

Well, not being sure if the 90% mix and lacquer will be compatible I add a few drops of Behlens fruitwood - I know that is compatible.  Just enough drops to turn the 90% alc. orange and where I couldn't see thru the jar.  Alright, let's add this to 400 cc of lacquer thinner in the spray cup.  Hmm. I get the feeling now I haven't done anything special for some reason. 

Next, fill up the rest of the spray cup with nitrocellulose lacquer.  Let the mix set awhile, like a day or two and commence to spraying.

Long story short, decent result but atomization could of been better but the coats {9-10} were thin enough to keep me out of trouble.  I went out and looked at one guitar that was sprayed and noticed one area on the wood binding that checked but the rest still looks pretty good.

For some reason the orange neoprene looking rubber on the guitar stands doesn't react with nitrocelluse but the black colored one do react with the finish - nothing that lacquer retarder on a cloth can't smooth out but still.

Link to comment
Share on other sites

  • 3 years later...

Resurrecting this old topic for whoever is interested. The French C2RMF (Centre de Recherche et de Restauration des Musées de France) published some interesting research. They were looking for an alternative to shellac for furniture restoration.

This is a link to the paper (in French, abstract in English):

https://journals.openedition.org/techne/6152#tocto2n6

Another link to the same information on their website:

https://c2rmf.fr/redecouverte-du-vernis-roubo-pour-le-mobilier-de-la-theorie-la-pratique

The abstract in English explains the goal of the research:

“Reflection on replacing traditional shellac varnishes with another finish began in 2002 at the C2RMF. The aim was to highlight the possible relationship between deterioration and the composition of the varnish, to assess the role played by protective coatings made of different ingredients on wood and, lastly, to study the long-term effects of light on woods thus varnished. The experiments conducted focused on a varnish described in L’Art du menuisier-ébéniste, published by André-Jacob Roubo in 1774. Several tests to measure thickness, appearance and mechanical properties were carried out on samples of veneer coated in the selected varnish. The encouraging results of its resistance to photo-oxidation and the oxygen in the air enabled us to establish a protocol for applying it to protect the surface of the metal marquetry furniture now in the Louvre.”

Based on the results, they selected two recipes. Just copied and pasted here, so in French, but should be easy to understand):

Recette 1
    •    100 ml de Butanone
    •    15,5 gr de Sandaraque
    •    6,2 gr de mastic en Larmes
    •    3,1 gr de gomme élémi
    •    3,1 gr d’essence d’aspic
 
Recette 2
    •    90 ml d’Isopropanol
    •    10 ml de Butanone
    •    15,5 gr de Sandaraque
    •    6,2 gr de mastic en Larmes
    •    3,1 gr de gomme élémi
    •    3,1 gr d’essence d’aspic
 

The first one is brushed on as a base coat. The second one is French polished on.

Link to comment
Share on other sites

On 10/25/2020 at 2:17 PM, Michael Darnton said:

Most spirit varnish possibilities that I could think of making without shellac would not be that great in some respect or other--usually a lack of even basic durability. Shellac is a really wonderful material in a way that other spirit-soluble resins aren't. In spirit varnishes shellac adds the same kind of tough flexibility that oil adds to oil varnish.

I always think back to Charles Reade's violin varnish treatise when there is discussion about shellac. His opinion of it was "A vile, flinty gum.", so it appears he didn't have very high regard for it's durability properties. I wonder if it was just the general opinion in those days, or if he really abhorred it that much?

Personally, I think it's a great varnish for many purposes.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.


×
×
  • Create New...