T 0014/83 (Vinylchlorid resins) of 07.06.1983

1. The question whether an invention has been disclosed sufficiently clearly and completely is not to be decided solely on the basis of the content of the claims. If a chemical invention involves the task of manufacturing a product with certain measurable properties (e.g. gel content or degree of polymerisation of a copolymer), and this task is performed by means of a process involving several variables, then the means of its performance are to be regarded as sufficiently disclosed within the meaning of Article 83 EPC if, encountering occasional lack of success notwithstanding strict adherence to the prescribed limits of those variables, clear information, contained in the description, regarding the effects of individual variables on the properties of the product enables the person skilled in the art to bring about the desired properties quickly and reliably in such an event.

2. If teaching thus disclosed cannot be defined in a claim precisely enough to rule out occasional failure, such a claim is not to be objected to, provided it is possible to deduce from the description the action to be taken - which also cannot be precisely defined - by way of fine tuning of the variables.