Wetgate Solution?


I have been watching your site off and on for a while and am starting to collect the parts with an eye towards constructing one early next year. I was wondering if you had considered a wetgate solution? My thought is to make the acrylic panels 24" tall instead of 12" and move everything except the first roller 6-8" higher. The first roller would be towards the bottom of the left panel and cut two slits on the sides to allow a small tupperware tub to fit under the roller which could be filled with film renew. Also, do you have a new parts list available for the upright version of the kinograph?


Actually a decision pro or contra a wetgate isn’t that simple.
From technical point of view it may be a good (but not the optimal) solution for digitisation, but archivists and restorers will tell you otherwise. The chemicals used for a wetgate may lead to faster decomposition of film.
And the film itself shell be considered as the first thing to save and not a digital copy of it.
The most prevalent chemical used in a wetgate is perchloroethylene and that is highly toxic.
To handle that chemical (as example in Germany) you must have a permission and guarantee that only especially trained personnel is working with it.
So ARRI uses another chemical for their wetgate which is called decalin. It is not known toxic.
But it is inferior to perchloroethylene because its refraction index differs from film a little more.
All scanner producers who I talked to, didn’t liked the idea of a wetgate solution and sell it only because some customers demand it.
In comparison with a dry scan a wetgate scan is not as sharp …but yes, it is cleaner.
Another method to remove dirt while keeping the image as sharp as possible is an infrared illumination pass.
But the dirty film parts can only be located and interpolated and are not original as with a wetgate.
Also an infrared illumination can’t be used in combination to black and white material, because silver isn’t transparent to infrared.
A wetgate can’t remove every dirt, so ARRI has also the ability to scan with wetgate and an infrared pass for the remaining dirt (on colour film).
There is also a new old method (old, because it is used in microscopy since 100 years) called dark field, bright field illumination with polarized light. That method can also be used with black and white material.
From technical and archivist point of view this dark field, bright field method would be the best, because it doesn’t damage the film, keeps sharpness as good as possible and can be used for black and white material.


Thanks Andreas. That’s got to be the best explanation I’ve seen of the pros and cons of using a wet gate. Since I’m just starting to collect the materials to build it, I think I will design it so that it can but doesn’t have to use it.