"Raw" linseed oil is just that - linseed oil mercilessly squeezed from flax seed and packaged with no additional additives or preservatives. Raw linseed oil dries very slowly, taking weeks to fully cure. You should limit its use to the insides of wood gutters, chopping blocks, sawhorses, and other items exposed to the elements where drying time is not an important consideration.
Slow drying is a mixed blessing. For oil-based paints and varnishes, slow drying is a benefit, since this allows the paint to "level" itself, giving a smoother finish with fewer brush marks. The best looking paint jobs are invariably oil paint jobs, without question. However, when used as a wood preservative for items that are handled or walked on, such as tool handles, furniture, or wood decks, long drying times are undesirable. 100% Pure, this slow drying oil has multiple uses. It helps wood retain its natural moisture, aids in water repellency, retards cracking, checking and shrinking.
"Boiled" linseed oil, though, is not boiled. The actual boiling of some varnish oils changes their drying characteristics. With linseed oil, though, it is the addition of certain solvents that causes linseed oil to dry more quickly, acting as if it were boiled. This makes it a better product for preserving tool handles, decks, and furniture. I suppose they should have named it "sort-of-boiled linseed oil", or "kinda-like-boiled-but-not-really-boiled linseed oil". Boiled Linseed Oil is used as a natural wood finish and preservative, either alone or with other oils and solvents. Mixed with oil based paints and varnishes, it increases gloss and improves leveling and durability. A mixture of 2 parts boiled linseed oil to one part turpentine creates a semi-gloss wood polish for furniture. Can also be mixed with mineral spirits.
Varnish can also be made at home. Our JD Homemade Varnish Recipe is an old Down East deck coating formula traditionally used on wooden decks for schooners, fishing boats, and porch decks. Makes for an amber finish. To customize the mixture, add more pine tar for a darker color or add less for a lighter color. Allow more drying time for the darker mixture. You will need 1 qt of Turpentine, 1 qt Boiled Linseed Oil, 1/2 pt Pine Tar, and 1/2 pt Japan Drier.