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PitsLamp
03-30-2013, 04:40 AM
I'm currently working with Rollei Black magic VC on cotton canvas for a client, but I ran into some problems.

I did test the emulsion before promising a client that I could deliver a canvas of 100x80cm. I tested a canvas of 50x50cm, it worked fine.

I precoat the canvas with the pure gelatine solution from Rollei, let it dry for a day, coat with the RBM VC, let it dry for about 4 hours.

As I said the 50x50 worked fine, because I could put in a tray to develop.

Here comes my problem:

When I process the 100x80cm standing while pouring the developer on the canvas, the solution comes loose in quite large chuncks. I have to process standing because I don't have enough room to process it laying down in a tray.

Now I read, I should use the hardener solution, but I'm confused about a couple of things:

- Should I add the hardener to the gelatine and the emulsion, or only to the emulsion?
- The manual of Rollei says that when hardener is used, the emulsion should be used within 2 hours, but I know my canvasses aren't dry in 2 hours, because of the gelatine I can't use a hair dryer. So do I have to use the emulsion within 2 hours or just leave it longer
- Should I also add some hardener to the developer if I'm using ilford paper developer?

- Also what's the best tool to pour out the chemicals on the canvas, so that it doesn't damage the solution?

Thx a lot for answering my questions and I hope I don't have to go looking for a large tray to process the canvas, because I want to go even bigger than 100x80cm.

PitsLamp
04-15-2013, 05:28 PM
An update, I'm still not very successful in printing the big canvas.

I tried several different things and there is progress:

By adding 5ml hardener to the photographic emulsion, the emulsion stays on the canvas. However according to the instructions of mahn, manufacturer of Rollei Black Magic, once you use hardener, you need to use the emulsion within 2 hours. However I'm getting strange results, below are some photos of my results.

First photo, used the emulsion after 1h45 of drying: results Streaks

67308

second photo, used the emulsion after 3h30 of drying: result strange "bubbles"
67309

third photo, used the emulsion after 1h of drying: everything fogged and heavy streaks

67310

Does anybody have any idea what the problem is and how I can solve it?

I tried contacting mahn.net, but after a week I still haven't gotten any answer of them.

jnanian
04-15-2013, 06:00 PM
hi pitslamp

have you tried putting the gelatin and hardener and emulsion on a piece of paper as a test
to see if it fogs or bubbles or streaks &c on the paper ?

--

is your emulsion fogged because of how + where it is drying ?
the glow from the blow dryer might fog ... and ambient + safe light too...


do you add a little wetting agent / surfactant / something like photo flo to the emulsion so it coats evenly ?
( several coats of the emulsion ) ?

have you tried to coat the canvas as you did before, but put hardener in the fixer or the developer bath rather than in the emulsion itself?
that might also help ... if you put the hardener in the developer it might allow you to put a second coat of gelatin and then 2 coats of emulsion on your canvas to make sure it is coated evenly and dries better.

instead of cascading the developer on the canvas have you tried to use a spray bottle and mist it?
or removing the canvas from the stretchers and see-sawing it in a smaller tray or dammed part of your sink ?


i have never printed on canvas before ... if you were asking about glass or plastic or black-metal or paper i would have a better answer .. sorry..
john

PitsLamp
04-16-2013, 02:01 AM
Hi jnanian,

thx for the tips.

all 3 tests are coated and dried in exactly the same circumstances. I put them in a self made drying cabinet that has been tested and has no light leaks. If I would use a dryer, the gelatine would melt, so that's not an option.

safe light is red like recommend by Mahn. Not even darkbrown.

I'm going to try the wetting agent in the emulsion for an more even coating and coat 2 times.

I have not tried to add the hardener to the developer yet. Will do that today. According to Mahn, you're not supposed to add it to the fixer, because of the long washing time, which would damage your emulsion. A
so I need developer early on in the process because otherwise the emulsion lifts during developing.

I tried misting the developer, but that doesn't give me an even coverage of the developer on the canvas.

I want to print on metal too, did you take any extra precautions like using a alkyd resin primer or just gelatine.

jnanian
04-16-2013, 08:12 AM
Hi jnanian,

thx for the tips.

all 3 tests are coated and dried in exactly the same circumstances. I put them in a self made drying cabinet that has been tested and has no light leaks. If I would use a dryer, the gelatine would melt, so that's not an option.

safe light is red like recommend by Mahn. Not even darkbrown.

I'm going to try the wetting agent in the emulsion for an more even coating and coat 2 times.

I have not tried to add the hardener to the developer yet. Will do that today. According to Mahn, you're not supposed to add it to the fixer, because of the long washing time, which would damage your emulsion. A
so I need developer early on in the process because otherwise the emulsion lifts during developing.

I tried misting the developer, but that doesn't give me an even coverage of the developer on the canvas.

I want to print on metal too, did you take any extra precautions like using a alkyd resin primer or just gelatine.

hi pitslamp:

do you have a large cold surface you put your canvas on post-coating ?
that might also help with your frilling issues. at least with glass it helps ...
and luckily you don't have to make sure your surface is level ... the cold
chills and sets the emulsion.

i would try going against what the manufacturer suggests and do a test with canvas with the hardener in the fixer instead of the developer.
and don't use stop bath. if you can find and alkali fixer with hardener that would do you well too ... liquid emulsions seem to like alkali
no matter what you will have extended washing times because of there being hardener in the mix. if you use fixer remover / perma wash you can cut your
washing time to a minimum.
make sure you use a COLD developer ...

for the metal, i get it coated with an enamel paint. the emulsion sticks right to it and there don't seem to be any problems ...


good luck with your tests !
john

Ghostman
06-12-2013, 08:00 AM
Hi PitsLamp,

Do you have an update on how this went? I have just coated a couple of 50X50cm canvases (and some smaller) and would like to garner any tips you might have on working with Black Magic and canvas.

markdouglas
08-14-2013, 05:07 PM
I don't do anything near as large, but I do use a hair dryer to dry the emulsion. The important thing is no heat! I can get a small print dry in a matter of a minute or two...

TheToadMen
09-10-2013, 07:50 AM
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