ITTF Document on treated long pimple rubbers
July 7, 2008Document from ITTF regarding the ban of certain pimple rubbers:
“Treated rubbers.
The authorisation of coverings has so far been given without any reference to playing properties - just physical dimensions, colour and gloss.
We have had this phenomenon with treated rubbers for some years, but it was when it began to be produced in factories that it really called for our attention.
Various methods have been used, from private exposure to sunlight and microwaves, via professional coating with glue or lacquer, to some more advanced and secret processes.
The end result was usually a reduced friction on the pimple tops, which could be easy to discover by moving a finger across. The problem was to find a more precise and reliable method.
We found a company in Germany that is able to measure micro friction on the pimples. This is utilizing highly professional equipment which is partly protected by patent.
This equipment is not suited for bringing into a playing hall. So the first phase - where we are now - was to stop treated rubbers from entering the List of Authorised Racket Coverings by introducing a minimum friction level for pimples-out rubbers.
Some preliminary tests seemed to indicate quite clearly that our rubbers could be divided in two groups - treated and normal ones - based on friction.
A resolution was accepted in Bremen last year. To avoid mistakes we had to measure all pimples-out rubbers, and we began this last autumn.
In Zagreb recently we discussed the results for 220 coverings, and it confirmed what we had seen earlier. The minimum level was then set to 25 microNewton (mN) for new coverings. The introduction date was set to 1. July 2008, meaning that the List should then not contain treated rubbers.
An overview over our 260 pimples-out coverings at present gives:
33 that have too low friction, i.e. less than 25 mN,
25 where the supplier has given instructions “no measurement”,
25 where we have had no answer after repeated messages; we are rounding up these now.
By this action we have said something about what kind of rubbers we want, and it will have the impact that it will not be so easy to buy treated rubbers. We have no other choice then to deal with all these above in the same manner.
However, there will always be some who might want to continue this one way or another, but we do not know how many. What to do then will depend on the size and nature of the problem.
Rubbers change over time, as we know. 25 mN on a new rubber may be around 15 mN after a couple of years under normal conditions.
We have seen a very simple device from a German factory consisting of four pieces of rubber each with a specific friction level. By sliding a ball over the samples it is fairly easy to get a rough idea about status. A problem could appear when we are close to established levels. This can be compared to checking gloss in a hall, where a referee gives his views and makes a decision.
Before we make more out of this, it would be good to have a better idea about the potential problem, and then see if we can attack it accordingly.
It seems to be important to some to be able to link this to long pimples only. However, the picture is more mixed as there are both short and long pimples here. See below.
8.6.2007.
