Because of the BLO thread I just left Wikipedia. My head hurts. It may not be one hundred percent accurate but there is plenty of technical info about, resins, urethanes,and polyurethanes. If you get the time, use the three words I just mentioned, one at a time, to search Wikipedia. It is very enlightening about the products we use.
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Wikipedia and polyurethane
- Thread starter Jake Debski
- Start date
Richard Baker
RIP
Jake, Couldn't you just take a couple aspirin and summarize it for us when your headache lets up? Just the parts relevant to wood finishes.
I'm no science writer Richard but.........
Resin is a plant product mainly from coniferous trees. It has many uses, but its use in varnishes and adhesives is of interest here. Today, more importantly, the term is used for synthetic substances of similar properties.
“A drying oil is an oil which hardens to a tough, solid film after a period of exposure to air. The term "drying" is actually somewhat of a misnomer, since the oil does not harden through the evaporation of water or other solvents, but through a chemical reaction in which oxygen is absorbed from the environment (autoxidation). Drying oils are a key component of oil paint and many varnishes. Some commonly used drying oils include linseed oil, tung oil, poppy seed oil, perilla oil and walnut oil.â€Â
“Urethanes - Ethyl carbamate (also called urethane) is a substance first prepared in the nineteenth century." When combined with resins it becomes a “finish†or more commonly a "varnish." "Urethane itself is: (NH2-COOC2H5) and is not a component of polyurethanes .â€Â
Polyurethane varnish is a hard, abrasion-resistant finish. Since “poly†does not penetrate the wood very deeply it is often combined with oils or “oil modified†to insure depth of penetration or (bite). Without this oil poly would flake off if dented, heated, or subjected to shock. It should be added here this is where the term "propitiatory resins and oils" enters the picture. Only the manufactures know exactly what is in that can.
This information is just a drop in the proverbial bucket. I 'm still unsure what the term “urethane oil†is in today's parlance. The old saw “even a blind squirrel finds an occasional nut†applies here. I'll keep looking and maybe I'll get lucky.
Resin is a plant product mainly from coniferous trees. It has many uses, but its use in varnishes and adhesives is of interest here. Today, more importantly, the term is used for synthetic substances of similar properties.
“A drying oil is an oil which hardens to a tough, solid film after a period of exposure to air. The term "drying" is actually somewhat of a misnomer, since the oil does not harden through the evaporation of water or other solvents, but through a chemical reaction in which oxygen is absorbed from the environment (autoxidation). Drying oils are a key component of oil paint and many varnishes. Some commonly used drying oils include linseed oil, tung oil, poppy seed oil, perilla oil and walnut oil.â€Â
“Urethanes - Ethyl carbamate (also called urethane) is a substance first prepared in the nineteenth century." When combined with resins it becomes a “finish†or more commonly a "varnish." "Urethane itself is: (NH2-COOC2H5) and is not a component of polyurethanes .â€Â
Polyurethane varnish is a hard, abrasion-resistant finish. Since “poly†does not penetrate the wood very deeply it is often combined with oils or “oil modified†to insure depth of penetration or (bite). Without this oil poly would flake off if dented, heated, or subjected to shock. It should be added here this is where the term "propitiatory resins and oils" enters the picture. Only the manufactures know exactly what is in that can.
This information is just a drop in the proverbial bucket. I 'm still unsure what the term “urethane oil†is in today's parlance. The old saw “even a blind squirrel finds an occasional nut†applies here. I'll keep looking and maybe I'll get lucky.
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Dear Jake,
You need more time on the couch or more time at the lathe and less time at the computer. As long is I follow the safety precautions on the label and as long as the product provides the finish I'm looking for I don't really worry about its chemistry.
You need more time on the couch or more time at the lathe and less time at the computer. As long is I follow the safety precautions on the label and as long as the product provides the finish I'm looking for I don't really worry about its chemistry.
I don't know what is worse for a headache. Breathing the fumes or reading about this stuff.......
I checked the MSDS and CAS info on some finishing products (a "urethane oil", salad bowl oil and danish oil). It was pretty eye opening.
One of the big things I noticed is that the actual percentage of resin / oil can be very variable. For example, salad bowl finish has 0 - 25% of a proprietary resin and oil modified urethane of 10 - 35%. Those are pretty broad ranges. Even when they tell you what's in there, you don't really know what you are actually getting.
Another thing I found is that mineral spirits is a major component, but they list three different types of mineral spirits in the MSDS for most of the products. When I checked the CAS numbers I found that mineral spirits can be Hydrotreated Light (which may or may not be the same as kerosene), Hydrotreated Heavy (which may or may not be the same as naptha) and Stoddard Solvet (Stoddard was a drycleaner in the early 1900s). I guess by this point I should have realized that the term mineral spirits could mean a lot of different things.
At least I now know that I need to be a lot more careful about what chemicals I am actually using to mix my own finishes if I want to get consistent results.
Ed
I checked the MSDS and CAS info on some finishing products (a "urethane oil", salad bowl oil and danish oil). It was pretty eye opening.
One of the big things I noticed is that the actual percentage of resin / oil can be very variable. For example, salad bowl finish has 0 - 25% of a proprietary resin and oil modified urethane of 10 - 35%. Those are pretty broad ranges. Even when they tell you what's in there, you don't really know what you are actually getting.
Another thing I found is that mineral spirits is a major component, but they list three different types of mineral spirits in the MSDS for most of the products. When I checked the CAS numbers I found that mineral spirits can be Hydrotreated Light (which may or may not be the same as kerosene), Hydrotreated Heavy (which may or may not be the same as naptha) and Stoddard Solvet (Stoddard was a drycleaner in the early 1900s). I guess by this point I should have realized that the term mineral spirits could mean a lot of different things.
At least I now know that I need to be a lot more careful about what chemicals I am actually using to mix my own finishes if I want to get consistent results.
Ed
nuturner said:Dear Jake,
You need more time on the couch or more time at the lathe and less time at the computer. As long is I follow the safety precautions on the label and as long as the product provides the finish I'm looking for I don't really worry about its chemistry.
You're right about more lathe time. I have and use my favorite finishes, but being open minded enough to know that there may be a better mousetrap I'm always willing to experiment. My quest for that one "sweet finish" will continue, as will my curiosity for the many unknowns of my world. My 65 year-old body houses an eight year-old's curious mind. And I would not have it any other way.
... My 65 year-old body houses an eight year-old's curious mind. And I would not have it any other way.
Thanks for understanding the tongue in cheek remark; devil made me do it.
I have a body that's a bit older than the one you describe but it houses a mind similar to yours. So I understand where you're anchored.
With respect to finishes, my efforts to achieve consistency have taken me through so much research that I've concluded:
1. If it's poly finish and I like it I stick with it. No need to experiment futher.
2. If it's a wax finish and I like it, I stick with it. .....
You get the picture.
I rarely try a new finish, unless it's recommended by an experienced turner.
I just want to turn, finish, deliver; and do it all over again.
I worked in the ink & coatings industry for a few years, and if R&D of finishes is any similar there is a lot of guess work and experimentation involved - just like we have all experienced in the shop 
. Digging through the chemical literature is fun and can provide some insight, but it's hard to get a complete picture without knowing all the proprietary addtivites & the whatfors & whys they were added.
A case in point - Robert Rosand suggests Sherwin Williams quick dry sanding sealer. They have a cocktail of all sorts of good stuff in there. While I could go figure out what everything likely does, it makes for a pretty great finish the way it is, so I probably won't bother.
. Digging through the chemical literature is fun and can provide some insight, but it's hard to get a complete picture without knowing all the proprietary addtivites & the whatfors & whys they were added. A case in point - Robert Rosand suggests Sherwin Williams quick dry sanding sealer. They have a cocktail of all sorts of good stuff in there. While I could go figure out what everything likely does, it makes for a pretty great finish the way it is, so I probably won't bother.
Richard Baker
RIP
Thanks Jake
Thanks Jake and y'all for the research summary. Sometimes when you know more than you did, it feels like you know less. Somewhere in various labs across the country are a couple or three hundred folks that know all this stuff completely, and two or three of those folks are woodturners in their spare time. We need to find those two or three guys and/or gals and have them explain it to us.
Thanks Jake and y'all for the research summary. Sometimes when you know more than you did, it feels like you know less. Somewhere in various labs across the country are a couple or three hundred folks that know all this stuff completely, and two or three of those folks are woodturners in their spare time. We need to find those two or three guys and/or gals and have them explain it to us.
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Ed_McDonnell said:
FWW did a piece, covered here fairly well, on the proportion of solids in various wipe-on finishes. I sometimes lower the viscosity with solvent, so I guess it doesn't make a huge difference to me. Nor does the solvent, which is just pollution in progress, not part of the finish. I can make it evaporate faster or slower by adding, and I think your viscosities are inverted, lower or higher weight "petroleum distillates."
The type of resin and proportion to oil is what counts.