Waterproofing from Smit & Zoon

According to Smit & Zoon, when developing waterproof articles everyone faces the same problem: where to start? It helps if you take into account the fact that waterproof leathers are made the same way as other leathers via neutralising, retanning and fatliquoring. Then there are the well-known differences such as longer running time, frequent washing cycles and metal-capping. One of the most notable differences is in the choice of the fatliquor. Choosing the right fatliquor is crucial when making a leather that feels, looks and wears like a standard article but protects the foot from water. Synthol WF 500 combines these factors. The leathers made can range from uppers with a firm handle to soft nappas. Even when a high amount of waterproofing is demanded, the resulting leathers remain comfortable to wear through their water vapour permeability. Synthol WF 500 is normally applied in two steps. The first step is a pre-fatliquor. The waterproofing effect can be further enhanced by the addition of a small percentage of Syncotan TL to this first step. For the main fatliquor Synthol WF is either applied alone or in combination with a small amount of natural raw oil for improved handle and grain relaxation. The temperature of the baths should be between 50-60°C. Successful application of Synthol WF 500 does not depend on a high pH in the neutralisation or in the fatliquor bath. It has a certain sensitivity to electrolytes and thorough washing before its application is necessary. Even better than washing is the prevention of a large amount of electrolytes and other unfixed products during the process. Smit & Zoon recommend that large variations in pH and temperature should be avoided throughout the process. This is achieved by retanning at 35-40°C and by adding acid slowly over a long period of time. Another product from Smit & Zoon, Polyol 808 adds specific characteristics to the leather: an unmatched combination of fibre relaxation and fullness; a silky and warm touch; extremely soft handle; and improved crease resistance and tight-grain. These properties also apply to Polyol LT 303, a related product. Polyol HS 808 is a liquid product of 90% active matter. Polyol LT 303 is a paste, containing 55% active matter. The difference in concentration and the specific make-up of each product have their effect on the leather. Comparing both products on a 1:1 basis one notices the very soft handle obtained with Polyol HS 808. Polyol LT 303, on the other hand, shows a more pronounced fullness. The fact that both products are based on similar ingredients should not deter you from combining them. By doing this you will be able to make a difference to your leather so that it stands out. Both Polyol LT 303 and Polyol HS 808 have a very deep lubricating effect. However, it would be wrong to conclude from this that the stability of these products is sufficiently high to use them in floats containing chrome or high amounts of electrolytes. The amphoteric nature of Polyol HS 808 provides delicate emulsifying properties. For soft uppers Polyol HS 808 could be your fatliquor of choice when it comes to finding the delicate balance between softness and grain tightness. It can be used in quantities up to 50% of the total amount of oils given. For garment and upholstery leathers Polyol HS 808 works well in combination with any of Smit & Zoon's soft fatliquors. Synthol YY 707 is the fatliquor of choice when it comes to those elegant light- weight leathers tanners strive to achieve.