Beeswax has two basic parts, crystallized and un-crystallized. Of the crystallized portion, an amount of 15-25% that varies with when and where the wax was made and on what bees were feeding, are the largest “pieces” and what provides most of the water repellent properties (perhaps molecules isn’t the proper terminology so I’ll call them crystals) These “crystals” are too large in their natural form to penetrate most wood fibers, an amount will penetrate pores and larger grain voids but not the wood fibers. When hot beeswax is applied to wood, it is the un-crystallized components that “wet” the wood but they provide only slight water repellency and almost no resistance to moisture passage. In order to achieve the maximum water repellence, the larger crystals must be in a layer of sufficient thickness and since they cannot penetrate the wood fibers, they must lay on top and therefore be a topical coating just like a varnish or paint but lacking the durability. If one reduces the crystal size by reducing the wax with a solvent like Xylene, Toluene or Turpentine, the smaller crystal size allows for somewhat of an increase in the amount of crystals that can penetrate the pores and other surface voids as well as allowing for a thinner film build – much the same results as is obtained when reducing Brazilian Palm wax (Carnauba) or Candelilla wax but all waxes require a minimum surface film thickness in order to achieve maximum water repellence.
The downside of any wax-base finish or finish with a wax content is the lack of a sufficient moisture barrier for exterior and other applications prone to cyclic moisture levels. The highest level of moisture resistance is found in microcrystalline paraffin wax provided the oil content is sufficient enough to plug the holes in the crystal structure but not so much as to disrupt the integrity of the surface film layer. However, when it comes to resistance to the passage of moisture, waxes provide about as much resistance as a window screen, microcrystalline paraffin ranks highest followed by Candellila, Carnauba then Beeswax. Thus is why the higher the wax content of Shellac, the lower its initial moisture resistance and the more rapidly the surface film integrity degrades, such is also why blending a wax with a curing oil is detrimental to the level of protection that can be achieved by the oil alone. One must also account for the fact that even with sufficient surface film thickness, Beeswax starts to become brittle at 65°F and the film begins to internally separate around 38°F which further reduces both its water and moisture resistance properties. On the other end, depending on the exact composition of the Beeswax, it can begin to get tacky/gummy at 70°F and weep at 85°F. Beeswax has a lot of uses but it’s far from optimal for a gunstock or other exterior wood finish applications.
Mark
