Thanks Ron

I will look at Jim Brownings site , this is interesting to me to say the least.

Quote Originally Posted by Photo Engineer View Post

There is more to it than just what I said.

The current 16" blade will contain about 50 ml of emulsion to coat a 16x20 area or about 12 ml / ft square plus waste at top and bottom and selvedge.

Now, the problems are these.

1. At 16" you need to pull evenly over 2 feet of length for a 16x20 + waste. This is hard but not impossible. And, the well must be filled to cover that surface area.

2. At 32", the amount of liquid would be 100 ml, but might need a larger than 2.5 cm (1") well to contain enough liquid.

3. The design at this time is for 5 mil on paper so to get more laydown the well must be larger.

4. At 32" the draw is nearly 4 feet long. It is hard enough to draw steadily for 2 feet and at 4 feet the waste would go way up!

This is why Kodak and others automated the doctor blade method above 8". You draw the paper under a stationary blade and over a roller to keep it tightly held, or you use a well with tension. Also, fastening down paper as you describe does not allow the paper to expand. It does by quite a bit when wet and therefore, as size goes up, the tension must be relieved. At the 16" size, I cannot tape the paper down fully, just tack it at the edges and as it begins to swell, I release the taped edges quickly or it will buckle. This does NOT happen with film.

The largest paper I have coated is 30x40 using Jim Browning's machine. Film was no problem, but paper caused some problems which had to be worked out. We finally made a succession of 30x40 sheets on paper at Jim's. I have one here as a souvenier.