British Museum leather dressing has been used by many conservators since its publication to protect and conserve leather.
Formulation.
The basic formulation is:
The first three ingredients are heated together, then added to the cold solvent and allowed to cool while constantly stirring. Care should be exercised, as the solvents are highly flammable and have low boiling points.
Variations.
There are several variations in the formulation.
Sometimes 60% of the lanolin was replaced by neatsfoot oil. 
One disadvantage of the solvent hexane is its tendency to evaporate rapidly. Before the fat/hexane mixture has been able to penetrate deep into the leather, the hexane evaporates to the surface of the leather, taking most of the fat with it. 
While beeswax prevents air pollutants from penetrating the leather, it does this by closing off the leather, thus disturbing the water balance and causing the leather to dry out. The cedarwood oil acts as a fungicide to further protect the leather.
In use.
The British Museum leather dressing was part of an elaborate leather conservation programme. Other steps entailed cleaning the leather, if necessary with soap and water, and applying an aqueous solution of 7% potassium lactate as a buffer. A warning was given about the dangers of using too much lactate, which made books sticky and could cause fungal growth. The books had to be absolutely dry when the leather dressing was applied.
The dressing would be applied sparingly and rubbed into the leather. After two days, the treated leather was polished with a soft cloth. Hard leathers can be soaked in a solution of one part British Museum leather dressing: three parts Stoddard solvent. 
British Museum leather dressing darkens leather, but it is a treatment with a good success record.
References.
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