Is there something I can coat glass with to hold cyanotype sensitizer?

J 3

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P.S. in camera cyanotype are possible as mentioned. Also direct positive cyantypes are possible. I've never heard of dire positive being fast enough to be practical in camera. There are a few color variations as well (beyond just staining the paper) but most of them are not colorfast. There is one variant that is kind of purplish that I think is durable. Lots of room for exploration.

As cyanotype is near UV photography, coated lenses should act slower than their f-stop rating.
 
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Michael Meacham

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Thanks for all the input. I've got chrome alum coming from B&S and I'll start my experimentation there.
 
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Michael Meacham

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If I don't want to make a 600ML batch of emulsion, like in McAllister's video, how much gelatin is needed for a single 8x10 plate?
 

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I made some recently without chrome alum and without oxcalic acid, it stuck to the plate and worked just fine and is still pretty hard. Perhaps instead of making a 8x10 plate you should make 1/4th batch so that would be a total of 150cc of fluid and 19.69g of gelatin ( so you have a little more than 1 plate). The biggest problem with this emulsion is bubbles on your plate and heating the emulsion ( and your plate! ) hot enough that it flows fast, a small amount of emulsion and a room temperature plate well, the emulsion turns solid faster than the time it takes to get it to all 4 corners. you might also consider 4x5 plates at first to see if you need to tweek your coat and recipe and methodology and ... good luck !
john
 

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In every 100 CC of solution (sensitizer), there should be 8 g of gelatin and just before coating add 5 ml of 10% Chrome Alum.

That is a good starting point for a formula.

PE
 
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Michael Meacham

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Tried coating my first plate today. Pretty much a disaster. The emulsion had no problem running off the edges of the plate, but would not spread over the plate. The amount called for by B&S was 40 drops for an 8x10, approximately 2Ml. It took at least 5Ml to have enough to cover and I had to use a brush to try and spread it. I had it at 115 degrees in a water bath. I added the chrome alum right before applying. The brush marks are not attractive. I thought about floating it, but it would take the entire batch to do that and if I added the hardener, I would have to use it up in about 45 mins. The glass was washed and dried, but seemed to resist the emulsion. Any suggestions?
 

koraks

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Perhaps prepare the glass like it is done for wet plate. Just washing and drying generally doesn't remove the last traces of oil/grease from glass; some polishing with calcium carbonate is in order. You may get away with using a solvent, but calcium carbonate is cheap, easy and doesn't evaporate.
 

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michael
did you heat your emulsion up in a double boiler so it was really really runny? the glass plate has to be super warm too because the gelatin will start to cool as soon as you put it on the plate. you need to wash the glass so water sheets off of it, if it hangs when you run water off of the glass take a course plastic bristle bruch and some baking soda or washing soda and scrub the glass and rinse it good when water sheets off ( doesn't hang on any spots ) you are good and clean. you will need to put more than 40 drops of emulsion on the plate. get a small container to pour from, put your emulsion in there and pour a big puddle on your warm glass plate. it will take practice to get it to go to all 4 corners and not down your arm.
good luck !
john
 
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Michael Meacham

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The water bath was at 115 degrees, the plates were at about 90 degrees. I will rewash until the water sheets off. I'm going to replace my scale as I don't trust it. After setting up on the glass for 24 hours, it tried one today and got a fair image, but it all washed off. After exposure, the plate was almost too hot to handle so I let it sit until it was about room temperature before washing, but the emulsion may have still been soft. Isn't the hardner supposed to prevent resoftening? Outside temp today in Phoenix, about 110.
 
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Michael Meacham

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Does anyone know if a full spectrum 6500 K Super Daylight t-8 fluorescent tube will produce enough UVA to work in a light box for cyanotypes. It starts at 400nm.
 

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Michael: I can't speak for your bulbs but why not use the sun ? It takes no time at all to use the rays from the sun, even in overcast weather, to make cyanotypes. It's the difference between 3 minutes and .. sometimes .. 4...
 
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Michael Meacham

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I've used the Sun for years now, but it changes so much with the time of day and the time of year and of course if I want to do anything at night I'm out of luck. I want to build a UV light box so I can get consistent results whenever I want.
 

J 3

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It's fairly easy to get UV bulbs in the T8 size. These should yield much faster times than daylight bulbs (which do have some UV but not a lot). You have to duplicate the effect of a multiple min exposure to direct sunlight in UV to expose a cyanotype. Dedicated UV bulbs help the process.
 

RalphLambrecht

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eggwhite or gelatin?
 
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Michael Meacham

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I have now acquired 2 Ft fixtures and T-8 UV bulbs, and I am proceeding to build my box.
Ralph, I am using gelatin, still working on the process. I had to get a new scale as my old one was not up to snuff for this.
 
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