That looks like a potato ricer being used for the noodling.
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That looks like a potato ricer being used for the noodling.
Here's more or less the same method:Quote:
Originally Posted by Photo Engineer
http://www.holowiki.com/HoloWiki/images/coatmeth.wmv
More on glass coating can be found here:
http://www.holographyforum.org/HoloW...oating_Methods
i hope every body takes a look at the coating methods shown at the holo forumQuote:
Originally Posted by Hologram
i pulled a meyer bar by hand every day for a few yrs-the machines are an eye opener
the various hand pouring methods and the use of tapes to control flows are most interesting as is the moulding method
of course the emulsion for holos must be strictly controled and we here don't have those concerns-or maybe we should
thank you hologram
vaya con dios
Oh yes, excellent! Thanks for posting these.
I was walking through a department store looking for emulsion making equipment earlier this week. It is amazing what you can find. I got a pair of stainless steel emulsion kettles really cheap (ok, they had 'coffee' and 'sugar' on the side for some strange reason...)
I also saw a device for making mashed potato and wondered if it would be a good emulsion noodle making device - and there it is in the photos, the very same item, with Mark squeezing his noodles :)
Steve
Quote:
Originally Posted by David A. Goldfarb
I have one of those too. I use it for its original purpose. Try it - it's great!
Steve.
This reminds me of the way I used to coat copper clad board for PCB manufacturing with photosensitive etch resist.
We had a machine which held the piece of board vertically and lowered it into a container of solution by means of a motor and a threaded rod. Once fully submerged, the motor was reversed and the board was slowly pulled out of the solution. It probably took about three minutes for a board similar to the size of plate shown here.
The result was a very thin even coating. I think this system would also work to coat glass plates. The disadvantage is that both sides of the plate would be coated but you could either clean it off afterwards or use a peelable release film on one side and peel it off after coating.
Steve.
Quote:
Originally Posted by Photo Engineer
I like this, photographic forensics!
I've just bought a pack of vintage glass plates on eBay. They were made by the Brittania works, later to become Ilford limited, so must be from the 1890s.
I bought them for historical interest only, the unused plates have been exposed to light years ago and are of no value, well so I thought so until now. Maybe they hold some secrets about 1890s production techniques!
After close inspection I can see that there is overspill along one edge, but the other edges are clean. Also there are streaks on the back - and an emulsion finger print!
I conclude, Watson, that the plates were hand coated as a whole plate and some of the emulsion must have run across the back during coating and stuck to the rear of the plate, where the maker dabbed his finger in it . The plates were later cut into quarter plate sizes with a glass cutter, leaving three clean edges and one covered in emulsion run off.
I've tried a few photos, although they are not easy to photograph, being very reflective. The first pic is the back of the plate. To the left of the vertical streak is the fingerprint, but on the actual plate these marks appear silvery, rather than brown. The other two pics show the edges, mucky edge on the left, clean on the right. Note the chips where the glass has been cut. These chips do not contain emulsion, except on the 'mucky' edge.
These plates must have been very silver rich. It looks like the silver salts have reverted back to the metal: is this possible? They are very shiny in places.
Steve
Answering a few questions here:
1. Yes it is a potato ricer. I thought I had mentioned that. Sorry. At Kodak we used heavy duty versions.
2. The posted URL shows the coating of a solvent. Silver halide in gelatin cannot be coated so triivally I assure you. It is much more viscouse. Also it takes several hours to dry. You should not use a hair dryer! It will blow the wet gelatin around and create puddles.
3. In hand coating emulsion does run across the back. This is seen if you look at the posted photos carefully. This is how you know you have an authentic hand made plate. The defects like that prove it.
4. Mark is a world reknown authority on this method! Do not confuse it with wet or dry plate collodion which are totally different. Mark does those too.
PE
Mark sent me the scans of the negative and print from the plates he coated. Here are the two samples. On the left is the negative and the right is the print. Note the coating defect in the corner due to being hand made.
PE
I drove myself nuts trying to coat plates when we were putting the 'Silver Gelatin' book together. The best results I had with pouring on were when I preheated the glass, enabling the emulsion to stay hot & hence very mobile. A bit of dilution might also help, but you don't want to sacrifice density.
Apart from that I got very good results by totally immersing the glass in a bath of emulsion, then lifting & draining to one corner. The backs of the plates were protected with adhesive film that was subsequently peeled away.
NB, Aurum, the publishers have told me they are printing another 1000 copies of the book (no updated version though). Apologies for commercial break.