So, you've made something out of reclaimed
wood.
Maybe it's a
fence made from reclaimed wood, or shingles for your goat's
shelter, made from free
pallets.
You're looking for something to waterproof your wood, to make your shit
last.
When you're using reclaimed woods, they're thirsty and soak up oils like a sponge.
Maybe... you don't want to use up all your nice oil on pallet wood.
Welcome to iodine values.
Iodine Value is a direct proportion of mono-and poly-unsaturated bonds within a fatty acid. (A fat or oil.)
IV is defined as the number of grams of iodine absorbed by 100g of fat.
It is a measure of the degree of UNsaturation.
Fully hydrogenated oils and waxes have an
IV of less than 1. They're extremely stable. Even when exposed to air, they will not react to form polymer structures or oxidize.
Oils/Fats with an IV
below 100 are known as 'Non-Drying Oils' - they will resist hardening, and will retain their slippery or liquid quality
Beeswax has an IV in the range of 6-16. While it's extremely stable when exposed to air, it may still harden a little over VERY long periods of time when exposed to open air. I'm talking a century or more.
Oils/Fats with an
IV above 130 are known as 'Drying Oils.' - When left out in a warm place with plenty of ventilation, drying oils will react with the chemicals in the air and form those polymer structures - hardening into a solid. Drying oils are very suitable for using in oil paints - and for treating wood for waterproofing.
The initial hardening will usually take 2-5 days, and then it will continue to cure for up to 6 months. A hardened coat can be picked up and manipulated, but it
should not have heavy things placed onto it until fully cured, or the oil may also stick to the heavy object.
A higher IV score means it cures faster. The oil readily reacts with oxygen and other components in the air to form hard polymer structures.
Remember: the higher the IV, the faster it hardens/cures when exposed to air & heat.
Walnut oil is sold as a drying oil, but takes a bit longer. Its IV is 132-162 - an average of 147
Safflower Seed oil is likewise sold as a drying oil. Its IV is 136-148 - an average of 142
Poppyseed oil's Iodine number is 140-158 - an average of 149
Tung Oil is 160 - 175 - an average of 167
Pure (raw) Linseed oil is around 155-205 - an average of 180
Boiled Linseed oil is 170-204 - an average of 187
Chia Seed oil is 209-211 - our highest IV oil with an average sitting at 210.
I would like to introduce:
Soybean oil.
Often sold as generic 'Vegetable oil' for a humble $8 per gallon.
Soybean oil's IV, is 124-139. An average IV of 131.5 - It scraped in as a 'drying oil' by the skin of its teeth in Iodine Values, but generally isn't considered one because the dry time is longer than a week.
Soybean oil already has an established place in the paint & varnish industry.
Link Link2
While it's rarely used on its own due to the slow dry times, it was often blended with other faster-drying (Higher-IV) oils to bulk them up without reducing the overall IV much.
Making your nice oil go further
So, let's say you have some boiled linseed oil. Very nice, it cost you $45 for 1 gallon.
You then buy 1 gallon of soybean oil for $8.
If you mix them together 1:1, you'll end up with 2 gallons of oil with an IV of approximately 159
Mix them 2:1 and you'll end up with an oil with an IV of approximately 145 - an average IV that is 3 points higher than Safflower Seed's average of 142.
So, you'll end up with 3 gallons of an 145 IV oil, and you'll have only spent approximately $61 (plus tax)
Downside: That oil coating will probably take between 4 and 7 days to dry. You'll want to do this when there's no rain for the next week or so.
For VERY thirsty woods, like reclaimed woods, mixing in soybean oil could help stretch the waterproofing protection without blitzing through all your nice oil.
Now.... will these calculations hold up in real life? Will the final oil be up to your standards of dry time and curing strength?
Only one way to find out!
(Maybe try it with smaller amounts of oil first, rather than gallons at a time...)
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