I thought it might be an idea to put a few blog posts which answer frequently asked questions and this has to be one of the most frequent.
Dry wood is like blotting paper and would soak up whatever you put on or in it. A breakfast bowl would soak up the milk which would then go rancid, not nice. We treat wood to seal the surface and make it less absorbent so that it can be used for food and washed afterwords.
You can treat wood with oils or waxes, waxes tend to sit on the surface whereas oils tend to penetrate deeper. Oils can be separated into those which cure or set and those which always stay liquid. The ones which set are best partly because a cured oil protects the wood better, waterproofing the surface and not washing out, but also because an oil that always stays liquid like olive for instance can go rancid.
The three most common oils which set on their own are linseed, walnut and tung oil. Linseed and walnut have both been used as the carrier oil in oil paintings from the middle ages and it is the oil curing which sets the paint. Tung oil, made from a tropical nut, is commonly used in commercial finished like danish oil which is basically a mix of tung oil (expensive) with white spirit (cheap) the white spirit makes the oil thinner and helps it penetrate the wood. Warming the oil has the same effect but without adding unpleasant chemicals.
Since I know what a field of linseed or a walnut plantation look like and they are traditional in Europe these are may favourite oils. I advise folk who just want to treat a bowl at home to use walnut, it is sold everywhere you buy olive oil and makes a nice salad dressing too. The oil comes in a glass bottle and I suggest standing this bottle in hot water for a few minutes to warm the oil, pour it onto the wood and wipe around with a piece of kitchen paper, allow it to soak in for a minute or two then wipe off any excess with clean kitchen paper.
Unfortunately I can not use it commercially due to nut allergy so I use linseed. DIY shops sell raw and boiled linseed, boiled has metal drying agents added which are poisonous (a bit like old lead based paints) it is fine for cricket bats or window frames but not for food use. The drying agents mean that it sets in a couple of days rather than weeks.
So raw linseed is the stuff and liking to source things locally and organically I would ideally like to find a UK farm or oil mill where I could buy cold pressed organic oil. So far I have not found this so I use a really nice linseed which a friend buys for me in Sweden. Over there linseed is sold like olive oil here, there are so many different choices available. I like my oil because it is almost colourless where many linseed oils are very yellow. It costs more than a good extra virgin olive oil even buying it 20 litres at a time but it is worth it.
All my woodware is treated with this oil, the dry wood soaks it up and with time it sets in the wood and no further treatment is necessary. At home we never re oil any of our plates and bowl, just use them wash them in hot water with detergent and let them dry. If you want to keep your bowls looking bright and fresh then an occasional wipe with walnut oil will do the job.
One last comment, many commercial oils such as IKEAs chopping board oil are based on "mineral oil" or liquid paraffin oil. This is an inert oil so it never goes rancid but it never sets either. It is also a by product of the petrochemical industry, I prefer a natural vegetable based oil.
Hope this is helpful. Any other questions feel free to ask and I'll try to answer them here.
Now you know what to treat woodware with you might like to see the wooden bowls and plates that I make for everyday use.