I bought this device about 3 years ago and up until last winter the exposure times, using QLT universal photosensitive emulsion (two layers on the outer side of the frame, one on the inner side), have always been the same (4.5 minutes).
However, now the time seems to have increased significantly: in fact, after exposing the emulsion (bought just a few days previously) for 8 minutes, it tends to come off during the post-exposure wash, thus ruining the details of the image.
We’ve used a fresh emulsion to see if that makes a difference, but the issue persists. Do you have any advice?
From the information you’ve sent us, we can confidently say that if the emulsion is only a few days old, the issue isn’t related to the emulsion being old or out of date.
So, there must be another reason:
The first thought that comes to mind is the thickness of the layer of photosensitive emulsion: this could become an issue if there’s been a change of mesh count. Indeed, when the mesh count is lower, the layer of emulsion needs to be higher.
Consequently, the thicker the emulsion, the longer the exposure time needs to be.
To summarise, our suggestion would be to minimise the thickness of the emulsion as far as possible by finishing with a final backwards pass of the scoop coater, in so doing the scoop coater will collect and remove any excess emulsion.