I use linseed oil as a preservative to treat my wooden kitchenware. Initially, I thought one cold-pressed linseed oil couldn't be that different from another. If it's cold-pressed, it's cold-pressed. That's all I need to know, right? Wrong. Read on for some background on linseed oil production and a comparison between a cheap cold-pressed linseed oil and an expensive one from Sweden.
Linseed Oil Manufacturing
Swedish linseed oil manufacturers and various other people claim that the quality and clarity of the oil is dependent on the amount of UV light to which the seeds are exposed during ripening, meaning that flax plants grown in higher latitudes produce better oil. I admit I have not done enough reading to confirm this to be scientific fact but it is congruous with my meagre observations thus far.
It is also worth noting that the extraction process is very variable and it is probably not possible to determine the exact method from the label alone. The term 'cold-pressed' means that no heat is added during the extraction process. Less heat results in better quality oil. A significant amount of heat is generated by the pressing procedure itself. Some producers take extra steps to cool the system during extraction to keep the temperature low, thereby preserving the flavour and the fatty acids in the oil. The oil needs to be cleaned from the sludge and sterilised to obtain the final product, adding yet more room for variation.
Comparing Cheap Oil with Expensive Oil
When I started treating my wooden spoons with linseed oil, I bought a 1-gallon drum of Pegasus Health, food-grade, cold-pressed flaxseed oil for €20 (it turns out flaxseed oil is basically the food-industry's term for linseed oil: they're the same thing). The particular oil is British and is actually intended as a food supplement for horses. This oil worked satisfactorily well as a wood preservative for some time. It has, as I expected, a very slightly fishy, but not unpleasant aroma. In fact, some customers commented on the pleasantness of it (everyone seems to perceive the odour differently). However, I began to read about some folks choosing to buy expensive, organic linseed oil from Sweden and claiming that it was better for some reason so I tried it for myself.
I bought 1 gallon of Ållback, organic, cold-pressed linseed oil, produced in Sweden, for €87. In appearance, it is similar, but on closer inspection, it is noticeably clearer and has a more golden colour than the cheaper oil, which is a little turbid and has a slightly orange hue. When I removed the spoons from the hot oil after soaking, they had a positively mouth-watering, nutty aroma, which made me hungry. This, for me, is the most noticeable and pleasing difference between the two products and I think it's probably indicative of the high quality and purity of the oil generally. I have a tentative sense that the Swedish oil also dries somewhat quicker but I have not done any controlled experiments to confirm this.
In short, yes, expensive linseed oil from Sweden is better than the cheap stuff. And yes, in my opinion, it is worth the extra cash. Since flax grows well in the Irish/UK climate, it is a bit of a shame to buy it from Sweden, but until I find an Irish or British producer of high quality oil, I will be buying mine from Sweden. If anyone out there has a suggestion for a supplier, please let me know!
29/4/15 Edit - http://thelinseedfarm.co.uk has been suggested to me as a good UK supplier of linseed oil but I have not tried it yet.
7/4/18 Edit - Pre-oxidised linseed oils (like this one) seem to be more readily available now and they have the significant advantage of drying much quicker than the oils in this article which are not pre-oxidised (about 3 days versus maybe 6 months)