Making a double bass

[Michael_Molnar]

Circling back to the question of how to put color in the varnishes...

 

I've found that varnishes made from extended cooked down resins tend to be more fugitive than what you get with particulates...

 

Any thoughts?

 

E

Could you be more specific, namely about how the color changes?  What and how did you do to come to this conclusion?

[actonern]

I've moved my comments to another thread...

 

E

[joerobson]

Ernie,

I do not want to hijack Roger's very interesting thread.  But I do not want you to think I am ducking the question either.

Two thoughts come to mind.  First is that the color developed from the resin cook tends to be very light-fast.  Second:  Are you solving the varnish or using it as I make it?

if you like we can start a separate thread for this.

Joe

 

plus....what bulbs are in your light box?

[Melvin Goldsmith]

...

[fiddlecollector]

Well in my view i dont quite agree with this all colour coming from oxidiation /cooking of resin. Each to their own though.

I did do some tests of light fastness a few years back under uv and their was extensive bleaching of the colour, in one or two cases to almost colourless.

As much as i respect Raymond White i dont quite agree with his mention that all the colour comes from oxidation aging.The colour is just wrong and doesnt appear to correspond with oxidation/aging effects seen on other old objects of art.

I did find nitric acid induced colour to be alot less fugitive,probably due to the stability of the colour produced by the  sort of nitrating processes involved.

When i did organic chemistry proper nitration was always carried out in conjunction with both nitric and sulphuric acid ,so i`m  not exactly certain what these products that produce the colour in rosin resins is.

[Johnmasters]

Does the ferric chloride get netralized at some point? It's extremely caustic and I would be concerned about long term breakdown of the wood.

It is very dilute, .25% (Not 25%) and it is in a basic salt environment,  Calcium sulphate.  It is followed by two oxidizers,  the bichromate and hydrogen peroxide. These are both very dilute.  I don't know the actual chemistry,  hydrogen peroxide seems to sometimes act as a reducing agent (I think I read this,  I may be wrong).  I did not worry about this point.  The penetation is very shallow also.

[Bill Yacey]

I've been using this for years for etching printed circuit boards, albeit much stronger concentrations than 0.25%.

 

It was interesting that you mention this, because I often thought it might make a good stain if it wasn't for the corrosive properties. When making PC boards, I fish them out of the solution with a small maple stick. Over time the stick becomes spongy and eventually starts disintegrating.

 

My only concern in using it as a stain would be ensuring that somehow the ferric chloride becomes neutralized, Long term it may become a problem otherwise. Perhaps some of the other solutions you are applying are indeed neutralizing it, but I don't know enough about chemistry to venture an educated guess.

[Guest]

Roger

 

Do you treat, seal or apply anything to the inside of box?

[Berl Mendenhall]

I've been using this for years for etching printed circuit boards, albeit much stronger concentrations than 0.25%.

 

It was interesting that you mention this, because I often thought it might make a good stain if it wasn't for the corrosive properties. When making PC boards, I fish them out of the solution with a small maple stick. Over time the stick becomes spongy and eventually starts disintegrating.

 

My only concern in using it as a stain would be ensuring that somehow the ferric chloride becomes neutralized, Long term it may become a problem otherwise. Perhaps some of the other solutions you are applying are indeed neutralizing it, but I don't know enough about chemistry to venture an educated guess.

Bill I use to work at the Gould copper foil factory here in McConnelsville, Ohio.  We made the copper foil for printed circuits.  Japanese mining company bought them out and once they got the technology they closed the two factories here in the States and built their own somewhere else.

[Roger Hargrave]

Well in my view i dont quite agree with this all colour coming from oxidiation /cooking of resin. Each to their own though.

I did do some tests of light fastness a few years back under uv and their was extensive bleaching of the colour, in one or two cases to almost colourless.

As much as i respect Raymond White i dont quite agree with his mention that all the colour comes from oxidation aging.The colour is just wrong and doesnt appear to correspond with oxidation/aging effects seen on other old objects of art.

I did find nitric acid induced colour to be alot less fugitive,probably due to the stability of the colour produced by the  sort of nitrating processes involved.

When i did organic chemistry proper nitration was always carried out in conjunction with both nitric and sulphuric acid ,so i`m  not exactly certain what these products that produce the colour in rosin resins is.

 

I did not say that ALL the color came from cooking. I said that in most cases all of MY color comes from cooking. I said that White said that the red on the Seraphin came from oxidization. He also said that is was the result of time. How you then try to replicate this is up to you. As for cooking being less light fast, I doubt that. Lake colors in particular are notoriously fugitive. Moreover if you leave oil based mediums in the sun for any lenghth of time they will indeed bleach slightly, but they will also gradually change back if left in the dark; bleached colors will not. Personally I have made many colors over the past 40 years both alone and with others. I have also seen many colors that colleges have produced. Some come close but none replicate exactly that Cremonese look and you can be sure that given time they will all change. How they will change is impossible to say.  

[Roger Hargrave]

Roger

 

Do you treat, seal or apply anything to the inside of box?

 

I never treat the insides of my instruments. However, when I make a copy I often color them slightly, otherwise they look too light.

[fiddlecollector]

I did not say that ALL the color came from cooking. I said that in most cases all of MY color comes from cooking. I said that White said that the red on the Seraphin came from oxidization. He also said that is was the result of time. How you then try to replicate this is up to you. As for cooking being less light fast, I doubt that. Lake colors in particular are notoriously fugitive. Moreover if you leave oil based mediums in the sun for any lenghth of time they will indeed bleach slightly, but they will also gradually change back if left in the dark; bleached colors will not. Personally I have made many colors over the past 40 years both alone and with others. I have also seen many colors that colleges have produced. Some come close but none replicate exactly that Cremonese look and you can be sure that given time they will all change. How they will change is impossible to say.  

Hi Roger,

Sorry im speaking about this general view or latest fad for colour coming from cooked resin. I dont quite follow what Raymond White said about the Seraphin, the colour is just not right for the view that its all from oxidiation(havent seen the instrument you mention though assuming its the typical dark venetian red varnishes). Also you probably get slightly different processes going on depending on whether the resin is naturally aged ,cooked at high or low temps, treated with nitric acid or whatever else.

Many art books go on about how fugitive lakes are ,but some such as madder are quite fast and there are many examples in art of several centuries old that are still strongly coloured.Artists recommended that synthetic alizarin red was better than madder ,less fugitive etc. But that proved to be wrong, many sources now saying it is far more fugitive.

All i can say is that when i tested some cooked resins ,rosin and sanderac, when they subjected to high intensity UV to simulate a few years aging  ,they faded badly and remained so,these were tested alongside madder and cochineal lakes.

Many of the problems with lakes in old oil paintings are often linked to other things in the paint films .

Also natural materials are very varied in their chemical makeup and its very diffcult to get the same results twice when testing them ,like you say you can get 1001 results when making varnish from just 2-3 ingredients .

[Oded Kishony]

I've been wondering about the use of 'toned grounds'. Often a pigment such as raw umber or sienna were used to add color to the ground.

 

Wikipedia refers to this as imprimatura

 

I'm thinking that after a layer of clear mineral such as gypsum is rubbed into the wood a very diluted (with turpentine) solution of a translucent earth pigment can be either brushed or padded on.

 

comments?

 

Oded

[Oded Kishony]

 

Many art books go on about how fugitive lakes are, but some such as madder are quite fast and there are many examples in art of several centuries old that are still strongly coloured. Artists recommended that synthetic alizarin red was better than madder ,less fugitive etc. But that proved to be wrong, many sources now saying it is far more fugitive.

 

 

I think the reason that madder has the reputation for fading is because the color usually changes rather quickly, losing some of it's red components, after which it becomes very stable (in my experience). However, for an artist trying to adjust value and hue, this would be very disconcerting. For violin makers less so.

 

Oded

[robertdo]

I've been wondering about the use of 'toned grounds'. Often a pigment such as raw umber or sienna were used to add color to the ground.

 

Wikipedia refers to this as imprimatura

 

I'm thinking that after a layer of clear mineral such as gypsum is rubbed into the wood a very diluted (with turpentine) solution of a translucent earth pigment can be either brushed or padded on.

 

comments?

 

Oded

I rubbed some sunthickenend linseed oil mixed with maroccan ocre, burnt sienna, red ocre or cadmium red on the same maple rib piece before varnishing. I really like the look of the burnt sienna.

[fiddlecollector]

I think the reason that madder has the reputation for fading is because the color usually changes rather quickly, losing some of it's red components, after which it becomes very stable (in my experience). However, for an artist trying to adjust value and hue, this would be very disconcerting. For violin makers less so.

 

Oded

Yes Oded, i agree it usually looks more attractive which is what a violin maker wants as opposed to an artist. Artists often used to apply a glaze of madder or cochineal over an inorganic colour like cinnibar/vermillion. The lake usually fades but how much of this has to do with interaction of paint layers and how much is to do with just the effects of daylight. Madder lake can be very permanent in mediums other than oils for instance tempera.

[robertdo]

I seem to remember that the purpurin fraction (and maybe other minor fractions) of the madder root lake fades extremely quickly while the alizarin part is very lightfast

[fiddlecollector]

Robert ,i think its only one part  of the purpurin part thats fugitive .I cant recall at the moment whether its purpurin or pseudopurpurin that is pretty light fast, and when combined with the alizarin part of madder is responsible for natural madder lakes having a better lightfastness than alizarin alone,as in synthetic alizarin crimson.

I think Rogers thread is getting hijacked so i`ll shut up for now.

[Oded Kishony]

One of my concerns regarding a toned ground is that any colored pigment would look 'dirty' on the surface.

 

Oded

[robertdo]

Earlier this week I made some rust (vinegar and bleach on steel wool) and rubbed it dry on part of a garland I won't use. then I applied 2 layers of my varnish on top. the first layer soaked into the wood, the second seems to stay at the surface. But the look reminds me a little of what I saw sometimes on this forum when most varnish has worn on some violin. you can see the pores filled with the rust

 

[Michael_Molnar]

I am hesitant to use freshly made rust because it can be unstable and turn from your lovely red/brown to almost black. I am not a chemist, but I recall how the oxide was made largely determines its long-term stability. I suggest looking at the Kremer iron oxide pigments which are stable, very transparent, and beautiful. Also, contact John Schmidt in this forum for some of his transparent lovely transparent oxides. 

 

Mike

[robertdo]

You're right and I would definitely not use any freshly made rust on a violin. It just happened I had seen this recipe to make rust on internet and just wanted to have a go at it (and indeed if you leave the wool too long in the mix water/bleach/vinegar it goes black.

In fact one can get several different iron oxide with different colors if one want to try different shades of red or red brown.

I bought some nano iron oxide from Kremer. It's very useful to make completely transparent golden brown or orange (but too expensive to use the way I used the rust... )

[Johnmasters]

I've been using this for years for etching printed circuit boards, albeit much stronger concentrations than 0.25%.

 

It was interesting that you mention this, because I often thought it might make a good stain if it wasn't for the corrosive properties. When making PC boards, I fish them out of the solution with a small maple stick. Over time the stick becomes spongy and eventually starts disintegrating.

 

My only concern in using it as a stain would be ensuring that somehow the ferric chloride becomes neutralized, Long term it may become a problem otherwise. Perhaps some of the other solutions you are applying are indeed neutralizing it, but I don't know enough about chemistry to venture an educated guess.

At .25%  (not 25%) it is more of a developer.  It develops the pyrogallo somewhat like iron-tannin ink.  The dichromate helps too.  The hydrogen peroxide bleaches the pulp wood nicely.

 

I tried a lot of things and this works the best.  I don't know the function of dichromate,  but it works in .25% solution.

 

You can use the hydrogen peroxide directly after the plaster of paris/tannin-pyrogallo.  That works too.  I am not finalized on the easiest thing to do.

[Bill Yacey]

I'm interested in trying this, although I'm a little concerned about the dichromate; from what I read it's a carcinogen.

 

Are these solution percentages by weight?

[Guest]

I bought some rabbit urine that is used in hunting/trapping as a lure scent, The smell is atrocious and it is not yellow but green in color. I brushed it on some scrap maple and spruce and set it in the sun today. It turned a greyish color and the smell seems to have dissipated.

From what I've read so far rabbit urine can vary a lot in color. I will try and find some yellow urine to try next time. This green stuff I don't like so far...a fun experiment I just had to try...