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Simple in idea, not in the true world.
A reader of my weblog requested me to elucidate what polymerized oil is. So right here goes. On one stage the reason is extremely easy and on one other it’s consultant of all that makes ending and finishes so arduous to grasp. Let’s start with a definition of polymerization.
It is nothing greater than the best way sure finishes, together with oils and varnishes, treatment – that’s, change from a liquid to a tender or arduous strong. Oils treatment tender; varnishes treatment arduous. Polymerizing is just crosslinking. An entire bunch of monomers, that are single molecules, connect themselves to one another chemically to type polymers. That’s polymerization.
The most typical manner this occurs with oils and varnishes is by oxidation. Oxygen enters the end and causes the molecules to hook up, or crosslink. Metallic driers, which are sometimes bought individually as “Japan drier,” act as catalysts to hurry the drying. Boiled linseed oil and all varnishes, together with polyurethane varnish, have driers added by the producer. Raw linseed oil doesn’t have driers added, so this oil takes a really very long time to treatment – typically months, even with all the surplus eliminated.
Tung oil, the opposite widespread drying oil apart from linseed oil, doesn’t have driers added by the producer. But this oil dries quickly sufficient in order that it might probably perform as a wooden end. The caveat right here is that it’s a must to watch out if what you need is admittedly tung oil. Most of the merchandise labeled tung oil are literally varnish thinned about half with mineral spirits (paint thinner). Instead of drying tender and slowly, they dry arduous and way more quickly. If a thinner is listed on a container labeled “tung oil,” the product is thinned varnish.
It may assist to make a distinction between oils and varnishes that haven’t polymerized but and oils and varnishes which have had one thing completed to them by the producer to begin the polymerization. Using this distinction, we may create a class. Polymerized oils are these which have been partially polymerized so they may full their curing sooner when uncovered to air.
The drawback, as you’ll see, is that this doesn’t work nicely as a result of the finishes claiming partial polymerization are too totally different to suit right into a class. Nevertheless, that is the definition I’m going to make use of. Polymerized oils are these which have been partially polymerized – that’s, cured – earlier than they’re put into the containers.
Back within the early days of the woodworking renaissance within the 1970s, the phrase “polymerize” was tossed round quite a bit, normally to point that an oil, mostly Watco Danish Oil, cured or polymerized “in” the wooden somewhat than “on” the wooden. I bear in mind myself utilizing the phrase with shoppers to impress them. I had no thought what I used to be speaking about, however I used to be utilizing Danish oil, and “polymerize” made it appear particular.
Of course, that is foolish. All drying oils polymerize within the wooden as a result of they soak in and treatment.
Then a product known as polymerized tung oil began getting numerous consideration. It’s totally different than common tung oil as a result of it’s put via a cooking course of that modifications it chemically, making it treatment a lot sooner, more durable and glossier.
The course of begins by heating the oil to round 500° Fahrenheit in an oxygen-free, inert-gas surroundings till the oil begins to gel, then it’s rapidly cooled. This course of modifications the chemistry of the oil by inflicting the carbon atoms to crosslink (totally different from oxidizing) and thickens the oil significantly, so mineral spirits are added to make the product workable. More or much less thinner is added to create “low-lustre,” “medium-lustre” and “high-lustre” variations.
This end, Southerland Welles Polymerized Tung Oil, developed a following and I included it in each editions of “Understanding Wood Finishing.” To make it a class, somewhat than only a distinctive end, I mixed it with Tru-Oil, a gunstock end that I imagine to be linseed oil put via an identical cooking course of, although the corporate received’t verify this. At least, the 2 finishes act equally.
But the class then turned unwieldy, and that is a part of what makes the time period so complicated. In the early 1990s an organization known as Tried & True launched a number of merchandise it claimed had been polymerized. In truth, they’re little greater than uncooked linseed oil that has been uncovered to air for a time to begin the curing course of.
Though nonetheless technically “polymerized” by my definition, this product is about as totally different as it may be from the opposite two polymerized oils. They treatment quick and arduous if saved skinny. Tried & True cures a lot too slowly in my view to be helpful as a wooden end. It’s basically uncooked linseed oil.
It received its begin with a number of articles in Fine Woodworking touting its food-safe qualities as a result of it doesn’t comprise Japan driers, and that is precisely how the corporate represented it to me. As you could be conscious, my tackle meals security is that each one finishes are meals secure when totally cured.
To sum up, polymerization is just the best way oils and varnishes crosslink and treatment. Some producers start the polymerization earlier than placing the end within the container and name their finishes “polymerized oil.” But the merchandise promoted this fashion are too totally different to be included in the identical class. The result’s confusion.
A reader on my weblog prompt utilizing Tru-Oil to complete pens proper on the lathe – making use of the end like friction polish, holding the oil-damp fabric on the wooden to create warmth and pace the drying whereas the lathe is spinning.
I attempted each Southerland & Welles and Tru-Oil utilizing this technique, they usually labored moderately nicely. They dried slightly slower than friction polish, which is shellac. But they’ve the benefit over shellac and lacquer of manufacturing a way more sturdy (body-oil resistant) end as a result of they crosslink.
I assumed Tru-Oil labored higher as a result of it produces a greater construct and better gloss faster.
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