Newbie - Starting to coat paper

fdonadio

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Hello, all!


This is my first post in this forum, but I have been lurking for some time...

I am decided to start coating paper, since it's incredibly expensive here in Brazil. If all goes well, I'll be coating film in the future!

Initially, I will be working with 20 x 25 cm (approximately 8 x 10") sheets, but I intend on going larger, up until 50 x 60 cm (approximately 20 x 25").

I have some questions about emulsions and coating, for which I didn't find answers during my research here:

1. I will use this paper for enlarging, not for contact printing. Do I have to be careful with my choice of emulsion formula?

2. I prefer tonal neutrality and medium to hard contrast. Recommendations?

3. I intend on using chemigram techniques (like "painting" with developer). Would sponges or brushes scratch or peel the emulsion during processing? Should I try to use some hardener (chrome alum?) to avoid that?

4. I would like my DIY paper to look like satin or matte commercial paper. I don't like gloss. Though, I would like the emulsion to be as smooth as possible. Any recommendations on paper and/or emulsion?

5. Would an emulsion well and puddle-pusher be suited for coating 20" wide paper?

6. Wet or dry coating? When to use which?

Well... I think that's more than enough for now. I hope I am not asking too many questions...


Regards,
Flavio
 

Ian Grant

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Your best bet would be to step up use large format and print Platinum/Palladium. (Or make enlarged digital inter-negatives).

I made & coated emulsions commercially for a few years. I think if I had to make a choice now I'd make Kallitypes and Plat/Pall prints rather than coat my own Silver halide papers. If I scaled up and had a coating line then I'd coat my own fibre based papers. it's easy to coat and get excellent results with Kallitype or Plat/Pall and very repeatable and consistent.

All commercial papers are expensive these days but shop around buy from abroad, afctor in Import taxes etc. Foma papers are excellent and very good value but research where best to buy.

Ian
 

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I'll try some answers to your questions here:

1. I will use this paper for enlarging, not for contact printing. Do I have to be careful with my choice of emulsion formula?

>> YES. Some emulsions are too slow for enlarging and require long exposure times. Use an enlarging emulsion if possible. They are usually identified by the manufacturer or are marked as such if working from a formula.

2. I prefer tonal neutrality and medium to hard contrast. Recommendations?

>> Depends on the emulsion you are using and the developer.

3. I intend on using chemigram techniques (like "painting" with developer). Would sponges or brushes scratch or peel the emulsion during processing? Should I try to use some hardener (chrome alum?) to avoid that?

>> Without a hardener, you run a big risk of scratching or peeling. Use a hardener such as chrome alum or glyoxal. Glyoxal is often best on paper support while chrome alum is better on glass and some other surfaces.

4. I would like my DIY paper to look like satin or matte commercial paper. I don't like gloss. Though, I would like the emulsion to be as smooth as possible. Any recommendations on paper and/or emulsion?

>> Go to a local art supply store and examine some papers. When coated, the paper you are examining will become slightly more glossy but not overly so. I use Strathmore Smooth, but have found that any HOT PRESS paper of over 100# weight is needed to survive the process. I have used COLD PRESS paper, but it must be much higher in weight to survive.

5. Would an emulsion well and puddle-pusher be suited for coating 20" wide paper?

>> Yes, provided you can get and handle one. The coating process becomes more and more of an art, the larger the size.

6. Wet or dry coating? When to use which?

>> I'm not sure I know what you mean here. Sorry. If you mean when to use a coating - when wet or dry, with Silver Gelatin it is always intended to be used dry.

Good luck.

PE
 

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fdonadio

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PE,


Thanks for all the tips, especially about paper. I'll have to go to a good art supplies store and see/touch a lot of samples, I think.

I've been reading your posts for the last two months or so, but still didn't find a link to your book/DVD.

Some comments:

Photo Engineer said:
Without a hardener, you run a big risk of scratching or peeling. Use a hardener such as chrome alum or glyoxal. Glyoxal is often best on paper support while chrome alum is better on glass and some other surfaces.
Click to expand...

Yea, I've just read Denise's article on TLF (http://www.thelightfarm.com/cgi-bin/htmltutgen.py?content=22Jan2013) and she mentioned glyoxal. For sure, it will be hard to start coating with this, because the emulsion will be thicker... But I'll try that, eventually.

Photo Engineer said:
I'm not sure I know what you mean here. Sorry. If you mean when to use a coating - when wet or dry, with Silver Gelatin it is always intended to be used dry.
Click to expand...

Just check Denise's article. She soaks the paper sheet in water before putting it over glass and coating.


Regards,
Flavio
 
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fdonadio

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dwross said:
At the risk of disagreeing with #6 above, wet coating is the best way to coat large sheets. The size of the puddle pusher is the only limitation.
Click to expand...

Will any emulsion formula stick to the wet paper?

I am very interested in PE's Kodabromide-Brovira hybrid ((there was a url link here which no longer exists)), specially the grade 1-2 variation. PE also mentions an ISO washed variant, but didn't elaborate much...


Regards,
Flavio
 
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fdonadio

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Matt,


Both Denise and Ron know what they speak! THAT I'm sure!


Regards,
Flavio
 
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fdonadio

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Ian Grant said:
Your best bet would be to step up use large format and print Platinum/Palladium. (Or make enlarged digital inter-negatives).
Click to expand...

Thanks for the tips, but I am interested in silver-based emulsions. It seems more appropriate for me now.

I plan on trying some other techniques in the future. I even want to try daguerreotypes and other fancy/crazy stuff. But not now.


Regards,
Flavio
 

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Flavio, I was not sure what you meant in #6. Normally, Silver Gelatin is coated wet onto dry. Denise has suggested wet onto wet and has some excellent examples, and I have had workshop after workshop do wet onto dry and thus IMHO both are possible with proper work.

Emulsions will stick to either wet or dry paper, but it is a matter of working and learning.

The ISO washed variant requires that you use PA gelatin and this can be obtained from the Photographers Formulary, Kodak, or Roussellot. Using ISO wash, follow book instructions but with regular noodle washing the amount of sulfur (hypo) may change with water supply.

PE
 
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fdonadio

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PE,


Thanks again! These "little" details are very important and, most of the time, they are not simple, evident or both...

Photo Engineer said:
Emulsions will stick to either wet or dry paper, but it is a matter of working and learning.
Click to expand...

I was under the impression that wetting the paper would help against curling. That's the reason I asked in the first place... I forgot to mention that.


Well, I have some contacts at Gelita here in Brazil. They make several kinds of gelatin and should have the ones I need. I think I can even get some samples in a quantity that would last me for months!

I am evaluating some distillers, but they waste lot of water – 10 times the distilled water you get! :confused: Maybe it's cheaper to just buy DW.

Now I just have to study about washing procedures. Back to reading a little more!


Regards,
Flavio
 
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fdonadio

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PE,


I got a little lost about the ISO washing...


In another thread ((there was a url link here which no longer exists)) you state that "[w]hile coagulated, the emulsion can be easily washed by adding distilled water." Should I just wash the coagulum like I would do with the noodles?

I have looked around, but didn't find a foolproof explanation of the ISO washing process. I think I can understand the chemical process a little bit... I can't find "the DVD thread", which is supposed to have pictures of the ISO washing process... I am ordering your book in a couple of minutes!

In another news: I got a response from my contact at Gelita and they said they don't produce photo-grade gelatins in Brazil, but can get me pharmaceutical-grade or food-grade gelatins, in a wide range of BI's.


Regards,
Flavio
 

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Flavio, pharmaceutical grade is ok, but food grade is not. Also, PA gelatin is not made in pharmaceutical grade AFAIK. Gelita gelatin is a tad more active than Kodak or Rousellot, and so expect more speed and fog for a given set of conditions.

As far as ISO wash, basically, chill the emulsion and reduce the pH from about 7 to about 4 with dilute Sulfuric Acid and the emulsion coagulates into one large lump. Pouur off the water and wash the "lump" several times with cold DW. Then, bring the emulsion to a weight that is short of what you want with DW and gently warm it while adding Sodium Hydroxide solution. The emulsion melts and you have washed it of impurities.

As with any wash, test the wash water and it should be clear to be a good wash.

HOWEVER, if you overwash, you can cause fog.

Now, in production, we relied on either conductivity of the wash water or on vAg which is the voltage you get across test electrodes placed in the wash water. This prevents overwashing as you can wash to an exact value.

The attached photo is a frame from DVD #1 which shows the coagulum undergoing washing.

PE
 

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Photo Engineer

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As for coating wet or dry and paper curl. I have had no problems as long as I coat slowly and surely with a blade. This holds the paper down in front of the coating area and prevents curl. However, even without the weight, I have coated up to 30x40 sheets using Jim Browning's equipment.

Paper does tend to buckle, but if you coat dry and cold, the emulsion sets before the buckle can take place. If you coat wet, the process becomes very sloppy and the excess emulsion cannot be reused. With dry coating any excess can be reused.

You may want to try a wire wrapped rod for coating.

PE
 

dwross

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Ron,
You must not remember that I am not a sloppy person. Quite the opposite (often to a fault, I'm afraid. Artists shouldn't be afraid of a little creative mess. ) Fortunately, wet coating isn't sloppy. You might enjoy trying it at some point. It opens up a world of paper choices.

Your 4-inch blades are a marvel. No question. Unfortunately, you don't supply them any longer, and few people have access to Jim's coating machine. I use my glass emulsion wells about half the time, but I don't manufacture them either. Wet coating has the advantage of only requiring a coating rod. In addition, any paper can be used, no matter how thin, as long as it has a certain amount of wet strength.

One more point, and strictly my opinion based on my experience. Emulsion shouldn't be reused. One pass over dry paper and it picks up paper lint. This can show up as flaws and repellency spots on subsequent coatings. It only takes a little practice to figure out how much emulsion is needed for any given coating pass.

If anyone really wants to use an emulsion well, and has access to a good glass person, here are the instructions for making one. http://www.thelightfarm.com/cgi-bin/htmlgen.py?content=06Jan2012
 
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fdonadio

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Photo Engineer said:
Flavio, pharmaceutical grade is ok, but food grade is not. Also, PA gelatin is not made in pharmaceutical grade AFAIK. Gelita gelatin is a tad more active than Kodak or Rousellot, and so expect more speed and fog for a given set of conditions.
Click to expand...

Yes, I've read time and time again – in your posts – about food-grade not being adequate. And you're right: there's is no pharma-grade PA gelatin. Well, at least, not from Gelita. Kodak's gelatin business was bought by Rousselot back in 2011, so I am running out of options for sourcing the gelatins locally.

I am a perfectionist and, from my limited chemistry experience in high school, I was considering ISO washing, as it is a chemical process and seems to be more efficient. But, if I can't get PA gelatin, no deal!

Photo Engineer said:
Now, in production, we relied on either conductivity of the wash water or on vAg which is the voltage you get across test electrodes placed in the wash water. This prevents overwashing as you can wash to an exact value.
Click to expand...

I am considering a pH meter and a conductometer for my lab. I will have to buy a lot of expensive stuff (a decent scale, for example) and I want to have the best stuff I can get right from the start.

I can't thank you enough for your will to share your knowledge. I really appreciate.

Now I'm going to digest this information for a couple of weeks, as I plan my lab and source all the equipment and chemicals.


Regards,
Flavio
 
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fdonadio

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When I add H2SO4, it becomes part of the "lump", right? After washing, when I add NaOH, there will be a reaction that will result in Na2SO4 and water. That's why you recommended on adding "a weight that is short of what you want", right? Does the Sodium Sulphate interfere with emulsion quality or speed?

Regards,
Flavio
 

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in the 1800s when svg emulsions were invented there was the only 1 grade ...

http://www.thelightfarm.com/Map/Books/Osterman/MapTopic.htm


while my emulsion making chops are quite limited ( 28 years ago and none since )
for what it is worth, i have subbed glass and paper with food grade gelatin and did not get
poor results. maybe it is because it was just a binding layer to get the emulsion to stick
to glass or metal or paper or plexiglass, but just the same results were not disastrous.
you might consider using the pharma grade you can find locally, make a small batch of emulsion
and see if it works to your standards and if it does not work
import it from a supplier like art craft chemical or the formulary. they have photo-grade gelatin .


good luck !

john
 

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Denise, I have coated wet and dry both and still consider wet to be "sloppy". Reuse is useful when making test coatings so that you do not waste emulsion. It takes up to 40 ml to coat a 16x20 and that is expensive in anyone's book. Test first in the light with dyed gelatin. Go dark and do a small portion and reuse leftover emulsion if needed. Then coat your masterpiece.

PE
 
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fdonadio

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jnanian said:
you might consider using the pharma grade you can find locally, make a small batch of emulsion
and see if it works to your standards and if it does not work
Click to expand...

Thanks for the tip, John... My perfectionism, sometimes, leads me in a way that keeps me from trying simple ideas first and, then, progressing to more complex processes. I'm grateful that you tried to "wake" me up.

So, I'm in talks with Gelita's technical staff and they are about to send me some samples. I also contacted Rousselot and inquired about photo-grade gelatin, but my hopes are really low right now.

Did I mention I am a perfectionist? I am, so I'm also studying UF washing, which doesn't require PA gelatin, but opens a whole can of worms of its own... Oh, good grief!


Regards,
Flavio
 

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no problem flavio

being a perfectionist is a good thing.
but sometimes it can get in the way
of a good thing as well

good luck with your emulsion making !

john
 
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fdonadio

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Denise,

dwross said:
If anyone really wants to use an emulsion well, and has access to a good glass person, here are the instructions for making one. http://www.thelightfarm.com/cgi-bin/htmlgen.py?content=06Jan2012
Click to expand...

Thanks for all the tips, including the emulsion-well construction instructions above.

Don't feel bad about Ron's comments. It's not his fault. Engineers are like this. That's why we get every process even more perfect over time. But I think his sloppometer needs some calibration.


Regards,
Flavio
 

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Coating a 16x20 sheet wet or a 30x40 sheet wet can get pretty sloppy. A lab coat is in order!

A trash can at the end of the coating table is also in order to catch the overrun, and some cleanup is to be expected along the edges.

For small sheets, under 8x10 roughly, there is quite a bit less mess.

In our GEH workshops, we teach up to 8 students for nearly one day, how to coat using brushes, rods with wire, puddle pushers, and blades and also show them wet vs dry. We also coated hot vs cold. I'll leave you to wonder which methods they picked.

PE
 

dwross

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Flavio,
Sloppometer. . I love it!

I have many engineers in my family. Love them all. I did my graduate work in the Dept of Bioresource Engineering at Oregon State Univ. You state things perfectly. We owe a lot to engineers. I do wish, though, for a magic wand that could break the link in the minds of many engineers that confuses perfectionism with one-size-fits all (with them choosing the size, of course!)

Ron,
I think you have a mistaken idea about wet coating. If you are using the right amount of emulsion, why would it run off the table? And if your piece of paper is wider than your coating rod, why would it run off the edges?
 
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