Internegative guide wanted

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I am looking to play with making some internegs, but I hate going in blind. Anyone know of a good guide to making these beasts?
 

Donald Miller

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Do you mean internegs to make enlarged black and white negatives or do you mean internegatives made from transparency material to create negatives for color printing?
 

clay

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Two approaches to look at: negative->interpositive->internegative

Here are some links:http://unblinkingeye.com/Articles/EnlargeNeg/enlargeneg.html
or
http://www.bostick-sullivan.com/Technical_papers/Stuart%20Melvin's%20Pyro%20System.html
or
http://www.bostick-sullivan.com/Tec.../Enlarged Negatives for Platinum Printing.htm

Or a one-step direct negative by reversal:


http://unblinkingeye.com/Articles/NbyR/nbyr.html


I have seen prints from negatives made by all four methods, and they look great. I have a feeling that a learning curve will be involved in any of the methods, so don't expect immediate gratification. But these methods will actually work.

I'm reluctant to mention this on APUG, but the lazy man's method that i have used very successfully is the scan/adjust/imagesetter neg output route ala Dan Burkholder. That said, I find it works best with a HUGE digital input file form a large format drum scan, and can sort of fall flat with small negatives. The thing is, I just like real, honest grain when I print small negs, and the diginegs give me this fakey looking psuedo-grain. So I am gearing up to use a modified Stuart Melvin approach for my small camera negs that I want to print in platinum. I'll let the forum know if I have any great insights or noticeable successes. Any failures will be buried and will never be mentioned in polite company again.
 

roy

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clay said:
So I am gearing up to use a modified Stuart Melvin approach for my small camera negs that I want to print in platinum.

I shall be pleased to learn how you get on. The few negs I have enlarged have been on Bergger BPFB 18 and the results have been encouraging; although for various reasons I have only made very few. I have the film and plan to make more. Stuart Melvin's process was one that I looked at and it seems to be successful but I did not go down that route.
 

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I've had that link (one-step direct negative by reversal: http://unblinkingeye.com/Articles/NbyR/nbyr.html) in my favorites for a year now, but for whatever reason haven't gotten around to seriously considering trying it. I'm glad you reminded me. I have sodium sulfite, of course, and even potassium dichromate (for gums, which I haven't done yet), but where would one get sulphuric acid? Could it possibly be had locally, or would one have to order it online?
 

Aurore

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"swimming pool acid is the same thing. You can get it at any swimming pool supply place. They sell it by the gallon, and often in a two gallon pack."

You know, that's what I thought. I'm helping my mother get ready to sell her house, and the last owners turned the carport into a lanai... unfortunately, the carport cement had been painted green, so now the walkway and driveway are bare cement, but one strip of the walkway is partially green with old paint. I was pretty sure sulphuric acid was what we needed to etch the cement with... guess I can split the cost with her. :smile: Cool.

As far as battery acid, well, I think I'd rather buy the pool stuff. Must be psychological... same stuff, but somehow pool acid sounds safer than battery acid... :roll:
 

Ed Sukach

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The last time I bought acid at a swimming pool supply outfit - to adjust ph in the pool... It was Hydrochloric ... not Sulphuric. Does that make a difference?
 

Aurore

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Well, I called my mother, and she said it was indeed sulfuric acid that we needed for the cement, but just to be sure, I looked up 'pool acid' online.

"IDENTIFICATION OF PRODUCT
Product Name: POOL ACID
Common Chemical Names: 40% Sulfuric Acid Solution, Pool Acid
Chemical Names of Ingredients: Sulfuric Acid, Water
Chemical Family: Inorganic Acid Compound
CAS Registry Number: 7681-52-9
Empirical Formula: H2SO4
Molecular Weight: 98.0"

I got that from a 'material safety data sheet' pdf posted on a pool products manafacturers website.

But I'm glad I checked. :wink:
 

glbeas

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Aurore said:
"swimming pool acid is the same thing. You can get it at any swimming pool supply place. They sell it by the gallon, and often in a two gallon pack."

You know, that's what I thought. I'm helping my mother get ready to sell her house, and the last owners turned the carport into a lanai... unfortunately, the carport cement had been painted green, so now the walkway and driveway are bare cement, but one strip of the walkway is partially green with old paint. I was pretty sure sulphuric acid was what we needed to etch the cement with... guess I can split the cost with her. :smile: Cool.

As far as battery acid, well, I think I'd rather buy the pool stuff. Must be psychological... same stuff, but somehow pool acid sounds safer than battery acid... :roll:

It may well be safer to rent a 5000 psi pressure sprayer and simply blast the paint away. Be careful though, I've seen one cut a hole in asphalt so don't point the sprayer at anything that don't need spraying. Especially at people. Going over all the concrete will make everything look more consistent.
 

Aurore

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"It may well be safer to rent a 5000 psi pressure sprayer and simply blast the paint away. Be careful though, I've seen one cut a hole in asphalt so don't point the sprayer at anything that don't need spraying. Especially at people. Going over all the concrete will make everything look more consistent."

Already done it! That's why I said 'partly' green... some of the paint came up, but not all. We did it with the 1 degree nozzle, not sure of the psi. It was a rental from Home Depot.

Thanks for all the info. I will talk to somebody at the store when I buy and will certainly be careful. The potassium dichromate is probably pretty much the same when it comes to safety, and I have the neccessary gloves, safety glasses, and respirator. Should be fun :roll:
 

glbeas

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Aurore said:
"It may well be safer to rent a 5000 psi pressure sprayer and simply blast the paint away. Be careful though, I've seen one cut a hole in asphalt so don't point the sprayer at anything that don't need spraying. Especially at people. Going over all the concrete will make everything look more consistent."

Already done it! That's why I said 'partly' green... some of the paint came up, but not all. We did it with the 1 degree nozzle, not sure of the psi. It was a rental from Home Depot.

Thanks for all the info. I will talk to somebody at the store when I buy and will certainly be careful. The potassium dichromate is probably pretty much the same when it comes to safety, and I have the neccessary gloves, safety glasses, and respirator. Should be fun :roll:

It was probably quite a bit less psi. The 5000 psi machines can darn near take the paint off a car. After the acid soak don't just turn the hose on it to wash it off, that'll splash the acid all over. Mist it down or use a neutralizing chemical before hitting it hard. Good luck!
 

Aurore

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Well, since we're on the topic anyhow, think it'll get the rest of the paint off? The suggestion from the Home Depot employee was to re-paint... the etching was suggested as a 'primer' before repainting. But I was kind of hoping it would just take the horrible paint off. I stand to benefit... this is something I sometimes do for a living (when certain friends need the help), and she will certainly be paying me once the house is sold! :wink:
 

glbeas

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Wouldn't hurt to try it. If it doesn't work you can rent a sandblaster to take the rest of the paint off. While you're at it you can sandblast some glass for a light table or two for the darkroom.
 

fhovie

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Funny thing about chemicals - i know that pool acid i used in the past was an imprecise blended hydrochloric -. I also know that battery acid i used as a mechanic was a clean sulfuric - for use in distilled water. I would not make any assumptions. I did find out that the soda ash I was buying for my pool was anhydrous 100% sodium carbonate, that stuff I am using in photo chemistry - I did hunt down the MSDS on the BRAND of chemical I was using to find out though.
 
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