Kodak polycontrast filters with Ilford multigrade paper

[jnanian]

it never ceases to amaze me that so much of what we take for granted originated in rochester ...

[nworth]

No Ilford didn't copy Defender/Dupont



Dupont sold Defender Varigram, it's their trade name. Renwick of Ilford got there first with Multigrade, but Renwick had spent time with Dupont in the US, there were some trade links between Ilford & Dupont in the 20's & 30's, Dupont supplied film base to Ilford. The Multigrade patent was filed by Ilford in 1938, FF Renwick had worked on sensitizing dyes since the early 20's.

Multigrade was demonstrated to the Royal Photographic Society some time before it's release, but the outbreak of WWII and the take over of Ilford by the Air Ministry delayed the launch slightly so Varigram was marketed first..

The Defender Varigram was essentially the same emulsion and wholely based on Ilford technology, presumably under license from Ilford.

My guess is that the Varigram paper you used 45 years ago was improved compared to the original 1940 product, Ilford improved their version considerably.

Ian

The Varigam I used (first in 1955), was indeed a very much improved product over the original. From what I can determine, Varigam was also introduced in 1938. New technology is often introduced at about the same time by several manufacturers. As you say, there may have been some cooperative ties. But the original Multigrade was quite different than Varigam, both in performance and operation. It produced quite good prints, but the updated product introduced in the 50s was superior. The operational differences make me think that one or the other company was trying to avoid some patent issues. Maybe someone can look up the patents.

[Ian Grant]

Varigram was announced at the PSA Conference in 1940, the same year as Multigrade. Ilford research was downgraded during WWII, and Renwick died in 1943, Multigrade production ceased in 1945. When a second generation of Multigrade was introduced in 1953 it was quite a changed product.

Defender made significant improvements to Varigram a year or two later completely changing the way it was made, which is covered in a patent by Potter of Defender.

Ian

[Wade D]

Hmm, maybe I shouldn't have mentioned DuPont. :o The original question has been answered but I do find the ensuing discussion interesting.