I was putting some boiled linseed oil on a new jig when I slopped a little on my table saw. I also slopped some on my pants, but it'll probably wash out. Anyway, a thought occured to me. I wonder how this would work to protect cast iron from rusting? I normally use paste wax, but maybe linseed oil would last longer. Any thoughts?
Don
Spray'n'wash stain stick* works greatly for removing oils from cloth. But ya hafta lay it in a bit thickly. Not the liquid spray type and not any kind of "shout it out".
On the machine, consider camelia oil.
Alex
I'm guessing the oil will rub off.
Badly. Most oils become acidic on oxidising - it'll cause more rust than it stops.
linseed oil polymerizes
If it's boiled linseed, then it will indeed polymerize. However not all of it does so, and there will still be oxidation going on. Most commercial BLO's are also somewhat acidic anyway (which is why some peopel re-boil them with limestone chips to neutralised them).
Plain vegetable oils oxidise on exposure to the air and will cause acid corrosion problems on steels. There are a few that don't (camellia oil is pretty resistant to this), depending on the fats in the oil.
I don't believe that polymerization is the correct description of the curing process of BLO
"Drying oils, including linseed and tung, can be defined as liquid vegetable oils that, when applied in thin layers to a non-absorbent substrate, will dry in the air to form a solid film. This drying is a result of polymerisation by the action of atmospheric oxygen, i.e. autoxidation. "
see also
"Polymerisation" isn't really a description the process, so much as the end result. There are several ways for an oil or resin to do this, but it's reasonable to describe them all as a polymerisation -- it's not just the simple long-chain polymers like the reaction of ethylene to polyethylene.
In linseed oils, the amount of the oil that polymerises varies depending on the coating thickness and elapsed time. Raw linseed oil takes a week to air-dry, but not more than about 30% of it will have dried and little more does so in the future - several years later it still might not have reached the state that a boiled oil does. Boiled oils dry in around "a day". The rate of drying varies with temperature. Rate also varies with humidity, but this depends on the type of metallic drier used. Lead-dried oils dry faster in high humidity, manganese dried oils dry slower, or stop altogether at around 80% RH. A modern linseed oil finish may be simply unusable in an English winter.
The amount of oil that is polymerised in a "dried" oil varies with time, but mainly with coating thickness. As is well-known, an over-thick coating "doesn't dry". In fact it does, it dries as quickly as a thin coating, but the point at which it stops polymerising is less. The surface layer might polymerise, but beneath this is a layer of oil that stopped at around 50% - now unworkable and unremovable, but still mechanically weak. If the process merely _slowed_, it would be a lot easier to repair such finishes, we could just wait for them. As it is, even patience won't help us much.
A worst case for oil coating might be the making of oilcloth, where a fairly deep penetration of oil needs to be dried. This is one reason for sizing the cloth before oiling it - if you oil raw cloth it's too difficult to avoid oiling an over-deep layer that then refuses to dry in its lower depths. In a good oilcloth, 80% of the oil has dried after a few weeks and a "finished" cloth, 10% might dry over the next summer, and 10% never dries, remaining as a plasticiser ("never" means the useful lifetime of the cloth - after a century or two it does dry, and the now-brittle cloth will crack). Modern linseed with cobalt driers tend to dry more thoroughly than this, leading to a brittle cloth.
Iron compounds work as a drier for linseed, in that they cause it to dry more quickly than a raw oil. However they also _prevent_ full polymerisation of the oil. Even boiling your oil in an iron pot is enough to cause trouble with this and may lead to an oilcloth with a permanently sticky finish. Iron pigments have traditionally been added cold to finished oils, before coating the oilcloth. As well as a pigment, this may also have an effect in preserving the plasticiser content long-term. Being added cold, they have no effect on the oil as it dries immmediately in the couple of days after coating.
If you can find a copy, a useful text here is Leighou's "Chemistry of Engineering Materials" and the chapter on organic protective coatings. It's old enough (1942) that linseed oil is still a major economic material for paint and varnish making.
Oxidative cross-linking.
As what ? The mechanism for polymerisation, or are you taking the line that cross-linking reactions aren't polymerisations ?
I thought that was the definition of polymerisations...
Nope. This has to get the oxygen before the cross-linking can take place. Differs from normal polymerization reactions, in spite of curmudgeons. Chemical composition changed.
So is vulcanised rubber a polymer ? Some sources claim that it's only polymerisation if you're making a long chain molecule from repeated units. Randomly cross-linking a long natural-origin protein doesn't count.
(I don't hold this view myself)
hold with it? I can't even focus on it long enough to try and figure out some of those words/processes are...
It's only chemistry. It's all just "eye of newt and toe of bat", dressed up in a lab coat,
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