This might be of interest to some of our new shoemakers who didn’t have the opportunity of a long period of working/apprenticing with a master who hand welts and how he/she prepare the insoles and soles for inseaming and sole stitching, I can see how this preparations can be over-looked in a few weeks course on shoemaking. No welting process can be carried out well without mellowing the insoles and soles no matter what the tannig agent/s is, we all know leather is easy to cut when wet, The mellowing of leather for bottoming work is similar to that for Rolling/compressing, It is important that the water be clean, soft, and pure.
The first thing to do is wet the leather and care must be taken not to stain it by the iron in the water or the container the leather is immersed in,how long the leather is immersed, depends on the leather water resisting power, its substance, and what part of the hide, shoulders and bellies need less time in water than bend and butt,but the moisture must be allowed enough time to go to the centre and whole of the leather.
Here is how the good teacher, Mr Frank Plucknett describes the “mellowing” process;
“If an attempt be made to cut the leather which is just taken from the water, and than the leather is laid aside for some time- say tweleve hours- a second attempt is being made, it would be observed that the leather after standing could be cut with much greater ease, the reason being that although water had percolated between the fibres, yet the fibres and solid matter in the spaces were (previous to standing) still hard. If some water is poured on a basin of dried peas it quickly percolates between them, but the peas are not therefore soft, the water must now percolates into the dense body of the pea and this take some time. I n a similar manner the water quickly percolates between the fibres and around the masses of tanno-gelatine which fill the spaces, but it must continue its penetration into the fibres themselves and into the filling, until both are sufficiently plastic that they can be used, this will require some time and is known as “mellowing” the leather”.
The general practice is to wet the leather in the afternoon for few hours and than wrapped fully in paper (without print) and put in a dark spot to be used the next day, it shouldn’t be permitted to remain damp long enough to become mouldy.