See the full report by the Welsh Plant Breeding Station Plas Gogerddan, Aberystwyth (Great Britain).
The full 1987 report is available on the download. Unfortunately due to the age of this report only a scanned copy is available.
Crossing bags manufactured from three grades of polyester and three types of paper bags were tested for their permeability to grass pollen.
Bags were placed on L.perenne plants of known PGI isozyme genotype.
Any pollen passing through the crossing bag and pollinating the plant was detected by assaying its progeny for PGI isozymes. The results obtained allowed differentiation of the various materials for their suitability for pollen proofing.