Michael_Molnar

Cooked Rosin is Fugitive

Recommended Posts

I have long suspected (as well has other makers) that the cooked rosin is fugitive. Below is a photo of two samples of cooked rosin varnish. The control sample is labeled "AIR" because it was left in the air outside my UV drying cabinet. The test sample is labeled "UV" because it was placed for 12 hours in the UV cabinet. It is obvious that the varnish is fugitive.  The test sample received less UV intensity than my violin gets because the sample was on the door ledge out of direct illumination from the UV lamps. I believe that perhaps the only way to use cooked rosin is to reduce UV drying and resort to siccatives as @Roger Hargrave did. Of course, I wonder why mess with something so unstable and difficult to control. I'll have more to say on this topic. Stay Tuned.

 

147573234_UVFugitive.JPG.ba51a5f276a2349b25b2dd857de968da.JPG

Share this post


Link to post
Share on other sites

Micheal, color derived from heating the rosin certainly will go lighter upon exposure to UV.

However, the color change will "plateau" at some point, and then remain very stable. This is one of the things which makes heat-colored resins difficult to work with. There have been so many times when I thought I had "arrived" at the final color, only to find it was much too light with three more days of UV exposure.

Thanks for posting your experience, I think it's very valuable.

Share this post


Link to post
Share on other sites

Even the unfaded varnish looks too weak in color, assuming it's the very thick blob that it appears to be.  Applied thinly, I think it wouldn't look like much.  I could varnish a boat with all the stuff I have that looks fantastic in the jar, but just a light amber when applied.  Oh, well... there are good pigments and lakes out there.

 

Share this post


Link to post
Share on other sites
1 hour ago, David Burgess said:

Micheal, color derived from heating the rosin certainly will go lighter upon exposure to UV.

However, the color change will "plateau" at some point, and then remain very stable. This is one of the things which makes heat-colored resins difficult to work with. There have been so many times when I thought I had "arrived" at the final color, only to find it was much too light with three more days of UV exposure.

Thanks for posting your experience, I think it's very valuable.

The same is true for some organic dyes such as madder, the purpurin fades immediately but after that the color is very stable.

Share this post


Link to post
Share on other sites

Fugitive can be ok, as long as it's predictable, I'd use Joe Robsons Gold as an example, this is a coating that most are glad is fugitive in nature as it's scary gold/yellow, but once you know what it does , then it's ok.

I think most are too concerned about what violins look like "now" A large portion of what we see with older instruments is uv age in both the finish film and the top wood surface.

Like children,time goes by fast and the years under the sun changes things. I think a common path for a varnish object to take is to start out darker form the initial color loading in the varnish, then a "bleaching" effect happens where things lighten some, this phase can be pretty dramatic, depending on what you used. And then after about 10 years many times it reverses and things become darker again,lots of this gets into how much exposure it gets to light

Share this post


Link to post
Share on other sites
12 hours ago, jezzupe said:

Fugitive can be ok, as long as it's predictable, I'd use Joe Robsons Gold as an example, this is a coating that most are glad is fugitive in nature as it's scary gold/yellow, but once you know what it does , then it's ok.

The "color" we get from cooking...i.e.... processing....pine based resin is a function of what we begin with and how long and hot we process the material.  Mike's samples are quite blonde in terms of the possibilities.  I find them workable for color varnishes and varnish that one would add pigments to.  Darker cooked varnishes tend to hold their color as long as they are not over exposed to high intensity UV as they are first applied. 

The Gold that Jezzupe is refering to is the Aged Wood Gold color which is part of the Balsam Ground system.  There is a color which is a component of the minor degradation of hemi-cellulose which occurs naturally as wood is exposed to natural light.  This color cannot be extracted from wood.  In order to give us this color as a tool I researched plant extracts to find a plant which produced the same color.  I am able to extract this color but it comes with another color which is fortunately very fugitive.  After application exposure to UV or sunlight fades the wood to the color of aged wood. 

on we go,

Joe

 

awc gold sm.jpg

Share this post


Link to post
Share on other sites
14 minutes ago, joerobson said:

The "color" we get from cooking...i.e.... processing....pine based resin is a function of what we begin with and how long and hot we process the material.  Mike's samples are quite blonde in terms of the possibilities.  I find them workable for color varnishes and varnish that one would add pigments to.  Darker cooked varnishes tend to hold their color as long as they are not over exposed to high intensity UV as they are first applied. 

The Gold that Jezzupe is refering to is the Aged Wood Gold color which is part of the Balsam Ground system.  There is a color which is a component of the minor degradation of hemi-cellulose which occurs naturally as wood is exposed to natural light.  This color cannot be extracted from wood.  In order to give us this color as a tool I researched plant extracts to find a plant which produced the same color.  I am able to extract this color but it comes with another color which is fortunately very fugitive.  After application exposure to UV or sunlight fades the wood to the color of aged wood. 

on we go,

Joe

 

awc gold sm.jpg

Part of the awesome sauce collection

Share this post


Link to post
Share on other sites

Let me make some points.

Like many other makers, I came away from @Roger Hargrave's Making a Double Bass thread believing that cooked rosin could be used alone or nearly so. I was convinced that his description of the Serafin instruments pointed to a way to avoid using pigments. However, Stradivari et al. used pigments with cooked rosin. It appears to me that the cooked rosin augments the color, and works with other colorants, be they pigments or whatever. But, this relies on a strongly colored ground. So, I want to put a stake in the heart of this false notion about cooked rosin. 

Like Hargrave, I find that color must be infused into the wood and not on it. This color must be so strong so as to almost pass for a finished colored instrument. The worn areas of classical instruments are my proof for this assertion.

I am done for now, but have one more idea to test.

Stay tuned.

 

Share this post


Link to post
Share on other sites

Hi Michael,

The only thing that is fugitive is the volatiles . The rest stands BLACK for YEARS: in direct sunlight, snow, rain , dry days and ..... for years!!!

(test pieces still holding strong out in sun, rain, snow .... no change from 2010)

Cooked colophony  varnish is stable as *****

Roger H. is right! and black is black! (and pigment should be madder lake or none = my opinion, for more reddish  tint)

DarkVarnish.thumb.jpg.806b2a5899480b8acb2ad38da29ae4ab.jpg

DarkVarnish2.thumb.jpg.6ae120122aec067d8b97dd5bdaa297ca.jpg

 

 

Share this post


Link to post
Share on other sites

I'm sure if the ancients could have obtained the color density they desired, pigments wouldn't have ever been considered an option. However, even today, it's a balancing act in getting the right color, density and optical clarity.

Some things haven't changed all that much since those times; we still use natural resins and colorants using 400 year old recipes.

Share this post


Link to post
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.