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  1. Input needed colophony + nitrocellulose?

    Text states resins are added to provide surface adhesion which cellulose lacks, colors are generated using ordinary mineral and metal pigments. They even have a Tuscan Red!
  2. To Seal Or Not To Seal?

    Hope someone remembers a statement where Cremona inst's were relatively free of worm infestation, contrary to another region ( could be opposite of what I remember). Can infestation be from inside and reason for a coating?
  3. Cobalt dryer

    Hi Michael, it is from Protective and Decorative Coatings by Mattieillo. I've attached info on the contents of raw and burnt umber. Pigments like ochre or sienna have much more silica so produce more transparency to the varnish. Umbers do just about all you need. Hope you're busy with shopping for the holidays. fred
  4. Cobalt dryer

    Hi Uncle Duke, I was probably stating that if you are using umber pigment it contains manganese so no need for a drier. I use umber to color the varnish. I've attached some information on driers that for some reason isn't interested in attaching. fred
  5. What makes turpentine "bad" or "good"?

    Think law still allows up to 15% "other" ingredients like water, industrial solvents, etc. Some doesn't even smell like turp. Turp extracted from old stumps can't be labeled Gum Spirits of turp. Imagine Cremona turp, probably contained pine oil, methyl alcohol and other distillates I forgot
  6. Thinning varnish

    Hi E, (Ipr5184), Thank you for the kind words. Somewhere in the cooking it is possible to wind up with that more reddish than brown color that is so elusive. Hope you can capture it. I've wandered off the varnish trail on to the yellow ground path of frustration when I got the thought that Strad had money so he had a classy horse carriage equaling his status. Rereading Neal's 1833 varnish paper where he states " I got up a patent (Turner?) yellow pannel" could indicate this is a standard procedure undercoat prior to varnishing something like a horse carriage and could be familiar with inst makers. Turner Patent Yellow is made by mixing litharge and sea salt to produce lead oxy chloride. It cannot be purchased, you have to make it. I've made it but i I can't get the yellow since Kremer's litharge is reddish. Maybe go back to varnish frustrations- fred
  7. Thinning varnish

    Hi Weller, seems like adequate color, and it will probably clear up as stuff settles out. Now that yellow ground........ fred
  8. Thinning varnish

    Hi Weller, with umber our cooks are pretty similar except for jar height and cook length. Besides a lid smear it would be interesting if you can get color in 3 wipes on spruce. fred
  9. Thinning varnish

    Weller Williams, If you thin it with turp can you make a finger smear on the jar lid or any impervious surface to get an idea of drying time to tack free. It would help if you can write up your process for us, eg, how long the cook before and after reaching foam, how long at foam, color changes. Seems your jar is much taller than a 4 oz baby food jar that I use, so your cook retains a different mix than mine. My shorter jar allows the escape of contents with lower vapor pressures than your taller jar, and I include metals to generate colors, so our cooks are different. My lid smears are usually tack free in10-15 hrs. Interesting to see what your drying time is. fred
  10. Thinning varnish

    Morgana, we appreciate your response to posts, but I would suggest that your reply to Mike Danielson should have first been sent to our member Dr. Bruce Thai for comment. Most of us aren't much on chemistry and and I'm certain he would suggest you use Mike Danielson's post as a model, taking out chemical terminology wherever possible. fred
  11. Thinning varnish

    I think 1:1 resin/oil is near the limit of oil and still has reasonable hardness/minimum drying time. It is not a good idea to add oil after the varish is cooked since there is an interaction between oil and resin that does not occur. Also, unless it is boiled oil, with a drier, it could cause wrinkling in the finish. Turp vapors are heavy so they will sink after leaving your container, so caution. I frequently heat turp or varnish to reconstitute a varnish cause I use leaky baby food jars. If you have a skin on your mix I would do what was mentioned to discard for most likely it is air contaminated and insoluble. I note you didn't mention a drier in your varnish, this will extend drying time. That is a very nice cook, thin it with turp and hope you get sufficient color in few coats. fred
  12. Beady eyes... extreme version of fisheye

    Hi Don, just my opinion, adding a solvent to spread that stuff will ultimately give you a crackle finish when it leaves the mix. It looks like there is total surface tension and no surface adhesion, like water on a duck's back. fred
  13. Hi Michael- another problem for someone to tackle, for if you apply an umber varnish over reflective yellow it will trend to a red. I've tried Burnt Sienna that has no manganese, only iron, aluminates and silicates which give a transparent red, but not very strong. I do very little of anything, the old age infirmities have arrived. Hope all is well at your end. fred
  14. It is a common procedure when making an oil/resin varnish to apply heat to accelerate bonds in the oil to re-form to accept oxygen, interact oil and resin, and to shorten the time for the varnish to be tack free. While heating the mixture, a dab is usually dropped on glass, then touching it with a finger to pull a string of varnish which indicates state of the cook. Instead of this string method I've often advocated using surface foam as an indicator, heating high enough to build a stable foam, and when it sinks and surface clears it indicates no more reactions are occurring and to end the cook. I feel it is more reliable than string. However this requires a higher temperature and you have to remain nearby. Watching the change in the density of escaping vapor with temperature I realized it might be possible to use the vapor as temperature indicator to get to the pill stage. I selected where the distillates escaping created a light vapor which turned out to be a heating range of 395oF to 425oF. The heating time to get to the pill stage at this temperature took bout 8.5 hours, which is very good. Heating was stopped and started once during the process. The varnish consisted of 8g of Kremer linseed oil, 15g WW grade rosin (water white) and about an inch squeezed from Burnt Umber tube pigment all mixed at the start. After cooling it was thinned with turpentine to stick drip and smear on glass was tack free in 8-10 hours. The sequence of bead drops in the photo show the changes during heating, thickening so less tendency to flatten, becoming less tacky to ultimately tackles in bead 10. At this stage the surface was developing a skin around the rim indicating gelling of the oil. The heating could have been stopped at bead 9 which was slightly soft but tackles. The 3 smears on the glass show the deepening of the color with coats, and I think the final color on wood could be done in 3-4 coats. The heating set up is a 750 watt burner, a piece of aluminum flashing over the coil to help spread heat, a cut down can in case of any leakage, crumpled aluminum foil to plug the space in the outer bottom of the jar. The jar is a 4 oz baby food jar that are heat tempered. Distance from the surface of the contents to the opening of the jar has some significance in driving off substances creating tack in the finished varnish. In this set up only the very top was covered with a clear sticky substance, indicating most was blown off. With a taller container it would have remained and just refluxed in the jar and washed back into the varnish. Standing some brass screws and lining with shim stock, or copper sticks and flashing could mimic metal containers.
  15. JOHA oil varnish from International Violin Co.

    Sounds like the varnish lacks sufficient surface tension, ie, internal pull of the varnish to level itself. A varnish with adequate surface tension, you can make a smear and watch as it slowly levels and gets a uniform surface.