Abstract: There is provided a roll film assembly which comprises a length of photographic film having attached to each end thereof a length of backing paper, the film and the backing paper being wound together on a flanged spool, the backing paper being a laminate of paper and polyethylene which comprises as an opaqueing agent a layer of polyethylene which comprises from 7 to 10% by weight of carbon black particles of which from 20 to 100% by weight are conductive carbon particles.

Abstract: It is the object of this invention to provide a method for the preparation of an antiblocking agent which is effective in its antiblocking activity but is considerable less visible in photographic enlargements made from the film containing the antiblock of this invention.There is described a process for the preparation of monodispersed polymer particles between 5 and 10 microns in diameter which comprises preparing a dispersion of monosized seed polymer particles and then adding to this dispersion an ethylenically unsaturated monomer which is different from the monomer used to prepare the seed polymer particles, together with a polymerization initiator and completing the polymerization, the refractive index of one of the polymers produced being greater than 1.54 and the refractive index of the other polymer being less than 1.54.The refractive index of gelatin is 1.54. There is produced by the process of the present invention a particle which comprises two polymers.

Abstract: A diagnostic strip which comprises a base having coated thereon a dried layer which has been formed by coating onto the base an aqueous solution which comprises from 0.5 to 2.0% by weight of agarose and from 0.5 to 3.0% by weight of non-cross linked polyacrylamide or polyvinyl alcohol or a mixture of these polymers, the dried layer being 0.1 to 100 .mu.m thick and comprising 10 to 50% by weight solids.

Abstract: A method of preparing a diagnostic strip coated with agarose which comprises preparing a roll of web material so that an aqueous silver halide emulsion can adhere thereto on one side thereof, but which does not have a gelatin or any other proteinaceous layer on the prepared side then coating on the prepared side of the web by a continuous web coating method a layer of an aqueous agarose solution at a temperature of at least 40.degree. C., drying the coated agarose layer to provide a dried layer thickness of from 0.1 to 100 .mu.m which is dry to touch, but which comprises 10 to 50% w/w solids and cutting the coated web into strips of the required size.