I’m in the process of cleaning/restoring this old saddle. It has this white stuff that I couldn’t scrub off with saddle soap or water. It also has this gunk around the conchos. It sat in storage for a long time. It doesn’t smell musty or anything. Would love to know what it is and how to get rid of it.
Google “leather spew” and see if some of it matches what you are seeing. Around the metal components may be different - corrosion of the metal.
Heat it gently with a hair dryer and see if any of it will wipe off with a soft cloth. Then there is always diluted vinegar to try on an inconspicuous area.
Looks like old dried saddle soap.
Heard similar stuff called “ bloom”. Its wax and other products used in the tanning and conditioning process that sort of sweat up out of the leather over time,
You can get similar from over conditioning and using too much product as well. More I look at this, more I think its residue from cleaning products. Especially around the concho and under the cantle. Damp sponge with plain, clean water will take care of it. A soft toothbrush with plain, clean water can clear out tooling and that greasy dirt around the concho that could also be silver polish residue. Wipe with clean towel after sponging or brushing.