FredN

Members
  • Content count

    831
  • Joined

  • Last visited

About FredN

  • Rank
    Enthusiast

Profile Information

  • Location
    Falmouth

Recent Profile Visitors

5459 profile views
  1. FredN

    Making boiled linseed oil for use in varnish making

    A general comment on heating oils- I think you should consider you are working with two temperatures, you have a solution temperature of the vessel contents, and a plate temperature where a film of solution is briefly exposed to higher temperatures . If you are using an ordinary electric hotplate and, eg, direct contact between vessel and heat source the solution is briefly exposed to very high temperatures, possibly high enough to coordinate the bonds of the oil. Obviously, a heavy plate between container and hot plate would change this. Always nothing is clear and direct in varnish making-
  2. FredN

    Making boiled linseed oil for use in varnish making

    regards making an oil varnish, the standard rule is to heat body first, then air body when it is spread out as a film. In my earlier post, the statement getting to foam, is a simple indicator to get to a temperature where internal bonds of the oil are changing at a rate that you wouldn't have to wait, as a guess, a couple weeks if you were cooking at 100oC. If you cook OIL at over 650F I think you have around 30 minutes before you will have an insoluble rubbery gel. Essentially, you are speeding up the "drying" (time to get to gel) by heating. In the case of rosin, oil and resin should be cooked together because there is a chemical interchange.
  3. FredN

    Making boiled linseed oil for use in varnish making

    I know it is too easy, but a ratio of ca 2/3 oil/resin, one or two peas burnt umber pigment for drier and color, heat to foam (ca 575F) until foam dissipates (ca 35 minutes), cool, add trp. Tack free in ca 4-6 hours. Do you think they wasted time with mysterious varnishes?
  4. , I have a violin that you could say was soaked in linseed oil to a degree that the middle area of the bouts are almost transparent. It is the deadest inst one could imagine. If you scrape these areas it peels, no dust. I'm stuck on the idea they applied whatever was convenient to protect the inst from dirty hands. Wasn't washing a no no at that time?
  5. Just want to mention boiled and raw linseed oil behave quite differently. Raw linseed oil will absorb oxygen when expose to air and will swell forming large molecules, filling holes etc. Properly boiled linseed oil will just form the coat you apply.
  6. FredN

    High resin content varnish

    Hi Bill, that ends my thinking everything was found in the maker's shop. I guess if one has a good understanding of daily life during that period, they would have an idea of the extent of the availability and use of dyes. fred
  7. FredN

    High resin content varnish

    Hi Bill, thanks for the info. Any idea what wood was used for bows. Brazilin is found in a variety of tropical hardwoods.
  8. FredN

    High resin content varnish

    I'm stuck on the premise their varnish was made with only what was present in the shop; rosin, oil, dye from bow wood scraps, brazilin. I think if you are using rosin as the resin base of your oil varnish you should always heat it to get a thin surface foam to get your oil near gel phase so it will get to "tack free" in a shot time, and also, that text mentions that there is a chemical interaction between oil and resin when heated. Also acidity is reduced. When the foam starts to disappear the cook is complete. You could compare this procedure similar to getting a 10 inch string if you are someone who uses this method to determine when to end a cook. I also believe they used two varnishes, a clear short oil resin ground coat over a seal coat? (dye, glue, alkaline) containing driers to assure drying of the colored top coat. The radiance of the varnish is due to the reflective undercoat. I think this is the color maker of the overall varnish and its beauty. Without the radiance it is just another varnish.
  9. FredN

    High resin content varnish

    varnishes aren't true solutions, so it looks like you exceeded what the oil could hold, evident by adding turp and getting a varnish. I think you can go to any ratio as long as you consider your varnish after thinning. High resin ratios are chippy and don't like brushing. Just another possibility.
  10. FredN

    Reproducing varnish chipping.

    To get a brittle(hard) varnish could be short oil, metals, length of cook, resins, etc. To wind up with a crackle finish is usually due to the internal attraction of the varnish being greater to itself than its ability to adhere to the surface on which it is applied. If you make a smear of a varnish you just made on a non absorbing surface like a lid or glass you'll notice a thin ridge forming around the smear. This is caused by the internal attraction of the varnish film, and you'll also notice how this force also levels out the film. If you have a poorly prepared inst surface, something that doesn't like oil varnishes, you'll likely get a crackle finish. Industry has wrinkle/crackle finishes down to a science, producing an amazing array of predictable finishes.
  11. FredN

    Reproducing varnish chipping.

    My guess it is not a crackle finish, more likely a wrinkle finish caused by improper use of oil, swelling from oxygen uptake after applied. Also, another hundred possibilities. fred
  12. FredN

    Gluing centre joint

    Not quite on the subject but the best center joins and easiest I found was an MN tip to just clamp one half vertical in a vice, rub and set the other half and let gravity do the rest. I added driving nails on each end running some elastic bands around them. I once had to break and start again trying to use clamps.
  13. FredN

    Turpentine concecuenses

    Hi Tango- it depends on your purpose, if you just want to varnish an inst, use whatever works best for you. There are around 25 compounds in turpentine, a few have a low vapor pressure so it takes a long time for them to evaporate. Thinning an oil based varnish so it takes around 6 coats shouldn't be a problem. I've never tried Diamond G turp, but I'm pretty sure Joe R has experimented enough to know it is the only turp worth using. fred
  14. FredN

    turpentine

    Hi Joe, thanks for the description. I guess the word caustic is used as an unpleasant result. Thanks again fred
  15. FredN

    turpentine

    Carlo, sounds like you got your share of poor weather. Staying with varnish is a lot more frustrating, but safer- fred Hope someone can describe what they observe when the caustic reaction occurs. fred