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after the failure.. further advice appreciated!

chris77

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hello.
actually i would have liked to present you my first mural work, but the most silly of all mistakes happened (after extensive testing, setting up, etc..).
i was checking focus one last time, getting a bit excited, and during the exposure, already wondering about the luminosity - well.
forgot to stop down to the tested f11.. arrgh!

so, after cleaning off the sticky black gelatin, time to restart.

the surface (after cleaning) is wall paint and thanks to extensive scrubbing with a sponge rather matte.
in my opinion this surface would make the emulsion stick nicely (i dilute black magic with some more gelatin, spirit, and a few drops of wetting agent and spray it in layers).

BUT as PE mentioned, a dull surface is not helpful for good results, so i am considering to apply a base layer of... paint/acrylic/or else?

whats considered the ideal layer to work on?
i was also thinking about a thin layer of diluted acrylic binder, but i am not sure the cohesion will be good..?
or should i stick to the matte clean surface i have now and apply a glossy varnish in the end?

any help is highly appreciated!
thanks
chris
 
the good folks at liquid light suggest poly urethane as a sub layer sometimes. maybe you can find some matte surface
minwax poly urethane. i used to use this on glass all the time back when .. i was using a urethane sub layer. the only
downside is after a long while the urethane might have / has warmish yellowish tinge that might show through the image.
i have not coated anything that large or a wall, just very large sheets of glass. i painted regular old liquid light on with a sponge brush, nothing high tech.
i never watered things down, never used wetting agent and never added extra gelatin. just a layer of urethane, let it dry .. then the liquid emulsion.
but that was liquid light ( not vc or anything else ) maybe your emulsion is totally different and needs to be handled differently...


you might also consider doing a test on material like the wall you are going to paint on ... dry wall? and coat that with your sub layer and then
your emulsion and project the image from the same distance ... bottled emulsion has a relative iso like paper, liquid light is somewhere between 1-6 from what i remember ...
yours is probably similar ... so you can do a meter reading from your projector / enlarger / light source and get a print made on your test material so you can see
how it exposes and develops using your methods of coating, exposure, developing &c ... there is nothing worse than spending lots of $$ on materials, and lots of time on
a situation that doesn't pan - out
when i was doing extra large glass prints i would always make a small image on a broken piece of glass to make sure things worked right ...

good luck
john
 
Last edited by a moderator:
The newer "poly-acrylic" water based urethanes are water clear, but require several coats at achieve the coating thickness of the oil based ones.
 
check list

e.g.

item1
item2
...
stop down lens
...
itemn
itemn+1
 

hello.
thanks, you got some interesting points there.
i am hesitating to use polyurethan paint for health reasons. not that the chemicals used for developing (and fixing!) are healthy, but i am trying hard to keep pollution to the necessary minimum and use high quality breathing mask during application.
finding water based polyurethan paint in stores here in paris seems difficult..
 

you're welcome ...
many years ago I experimented with egg whites as a sub layer. it didn't work the way I was using them, but maybe you
can experiment using a mixture of egg whites and gelatin and a little bit of hardener
.... definately not fumes like urethane and you can make a nice Mayonnaise afterwards

good luck with your fun project !

john
 
You can get Baryta paste through pharmacists. It is used medically for X-Rays of the colon and esophagus. Mixed with gelatin and hardener it can be coated to make a white, glossy, reflective surface. You will need to mix it in a blender and then wait until the bubbles are gone. It will take some trial and error as well.

Once done, this should be a fine substrate.

PE
 

great info!
in this "formula" what is the function of the baryta paste? (trying to find more info.. how will i explain that in french if i dont even know what it really is?) can you explain it more please?
thanks a lot
chris


edit:
i guess this is what you are talking about...
http://en.wikipedia.org/wiki/Barium_sulfate

second edit:
well. now i get it. it is a reflector.
its easy to get as a powder. do you think its doable from powder? it wont dissolve in water, so the task will be to get it "dispersed" is it the right idea? staying water based?
 
Last edited by a moderator:

Exactly why acrylic water based varnish was invented--super low VOC's, no mask needed, no fumes.
 
Rick A said:
Exactly why acrylic water based varnish was invented--super low VOC's, no mask needed, no fumes.
Click to expand...

rick.
do you have experience (i mean positive results) coating emulsion on acrylic surface?
i am aiming for a perfect surface, well saturated.
as far as my experience goes the emulsion tends to peel off like skin. and applying the liquids can get complicated, as i am working vertically..
maybe you have a solution there.
chris
 
Baryta is a contrast agent in radiography and is the whitening agent in FB photo papers. It can be used from the paste + gelatin or you can get the powder and make the paste and add gelatin. Either way it forms a great whitening background.

I use baryta paper for a lot of my coatings. You can purchase it uncoated from Fotoimpex.

PE
 

hello PE!

i just come back from an artist supply shop with a kilo of bariumsulfat.
didnt understand what you mean by doing a paste?

wouldnt it be sufficient to:
heat up some water to make gelatin.
in another pot heat up some water and use a mixer to disperse the bariumsulfat powder, going for a rather thick but still fluid consistency.
then add gelatine until consistency seems ideal.
let cool off a little bit (50 °C)
add maybe 3 % of hardener (is it too little?)
some drops of wetting agent
and a cap of spirit to help getting lost of bubbles.
keep warm, not hot, and use directly..

did i miss something?

thanks again for your kind help.
one more question comes up.. what about PH, any problems possible?

many greetings!
chris
 
Do NOT add hardener until you are ready to coat the mixture!

Now, a paste might be about 60% baryta in 40% water.

The final mix should be about 10% gelatin, but IDK what the ratio of the two should be nor do I know what the covering power of your mix is going to be. It should be like white paint. You put it on and see no background material.

The pH should be neutral all on its own as all ingredients are near neutral.

PE
 

ok.
will try a first mix tomorrow and report back.
only question left is how much hardener to add just before application.
the only hardener i have got at home is the rbm5 by rollei.
i dont even know what the active ingredient is.. i am quite sure its not chrome alum.
maybe you know better..
 
Again, about 5 ml of 10% hardener per 100 - 200 ml of 10% gelatin used.

If it is blue, it is chrome alum. If it smells strong, then it is likely glyoxal or formalin. But, the hardener contents should be in their MSDS.

PE
 
Photo Engineer said:
Again, about 5 ml of 10% hardener per 100 - 200 ml of 10% gelatin used.

If it is blue, it is chrome alum. If it smells strong, then it is likely glyoxal or formalin. But, the hardener contents should be in their MSDS.

PE
Click to expand...

the rollei bm5 contains glutaraldehyd. i wonder if i can safely use it inside the flat.
considering that i use a spray gun to apply the liquids.
and of course i am building a kind of "tent" around the wall i am working on.

the mask i wear is definitely up to the task, but even after thorough air exchange (windows open over night) how many days/weeks will this stuff evaporate and at which concentration..

maybe i should rather switch to a less toxic hardener?
any advice on that?
 
Glutaraldehyde is pretty nasty stuff. There is no safe hardener, as they are designed to cross link proteins, and our lungs are made of proteins, so it is best to avoid inhaling the stuff. In solution they are ok.

I suggest spraying on the emulsion and then painting it afterward with a dilute hardener solution such as chrome alum. Let it sit for about 1 hour to dry and crosslink, and then rinse it off with some cool water. Then process.

Use a 5% - 10% solution of Chrome Alum.

PE
 
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