n. (also spue)a white, crystalline, waxy substance usually formed from fats or oils that precipitate out of leatherRoberts and Etherington 1982, 244spew. Material that exudes or is exuded. In the manufacture of leather, it is seen as a portion of the oily constituents of a leather that appears on the grain surface in the form of white crystalline fatty acids, or as a gummy deposit in the form of dark oxidized fatty acids.Alaska State Museum 2011The most common white stuff we have seen on Alaskan leather items is white bloom resulting from fats, oils, and waxes and may be referred to in the literature as ‘fatty bloom,’ ‘fat bloom,’ or ‘fatty spue (or spew)’. These terms all refer to the migration of fats/oils through the leather material that crystallize on the surface in the presence of air.Bell et al. 2017The white deposit is something called “spew” (or spue), also known as “leather bloom” or “fatty bloom.” Although this condition sounds serious (and disgusting), it’s actually a non-damaging reaction that occurs in some leathers which have been treated (or “dressed”) with different fatty or waxy compounds. When the leather is exposed to a change in climate, these unbound compounds migrate towards the surface and solidify, where they form a crystalline residue. This residue is the “spew.”Carrlee 2020This hide armor was treated with a leather dressing many decades ago to make it supple. Now that leather dressing is crystallizing out on the surface as “fatty bloom” or “spew.” It looks alarmingly similar to mold, but the deposits are quite waxy. It can be removed without much trouble, but it always comes back and there is no gentle way to fully remove it from the leather.
