VDB printing, critque and advice

[Ray Heath]

g'day all
i've been experimenting with VDB and cyanotype printing using inkjet negs

i have encountered several problems, OHP materials are expensive, not readily available and my printer ruins the surface during the printing

so, paper negs -
are they viable?

can i somehow reduce the extremely long exposure times? (3 hours for the attached image)

ideas?

suggestions?

the attached image was originally captured with a 10Mp Canon 400D digital SLR, the file was converted to B&W and adjusted using a simple curve in PS8 then output to a thin coated inkjet paper which was then contact printed to VDB on gelatin sized paper

re VDB-
size or not?

one or two coats of emulsion?

how determine enough exposure?

what causes bronzing?

how increase contrast?

[ann]

i have seen paper negatives coated with wax used for making bromoil prints, so it may be possible.

paper type will determine sizing, i have never sized paper for my vdb

we have used both types of coating in our workshops, and whether or not you use one or two coats is a personal opinon.

you need to do a step wedge to determine exposure times

there are several methods that can be used to increase contrast, the one that works best for our classes is to place about 10 drops of 10% solution of potassium dicromatic in a tray with about 2 liters of water before washing .

some people put the dichromate in the coating solution. we tried that way but find the bath version more effect.

[Don Bryant]

g'day all
i've been experimenting with VDB and cyanotype printing using inkjet negs

i have encountered several problems, OHP materials are expensive, not readily available and my printer ruins the surface during the printing

so, paper negs -
are they viable?

can i somehow reduce the extremely long exposure times? (3 hours for the attached image)

ideas?

suggestions?

the attached image was originally captured with a 10Mp Canon 400D digital SLR, the file was converted to B&W and adjusted using a simple curve in PS8 then output to a thin coated inkjet paper which was then contact printed to VDB on gelatin sized paper

re VDB-
size or not?

one or two coats of emulsion?

how determine enough exposure?

what causes bronzing?

how increase contrast?

Hi Ray,

Here are my thoughts about the questions you asked.

1) Size or not

I never size paper for VDB (as a matter of fact I only size paper for gum printing). What paper are you using to print on? There are several good papers you can use to print VDB. A very inexpensive but good paper is the new Weston Diploma Parchment.
http://www.crane.com/business/weston...palladium.aspx

2) one or two coats of emulsion

I always double coat VDB, however double coating will print slower but give better DMAX, IMO.

3) how determine enough exposure

With digital negatives you need to give the coated paper the minimum amount of exposure to get DMAX when printing the substrate

4) what causes bronzing?

Long exposures can cause bronzing or excessive moisture content in the emulsion

5) suggestions?

Inkjet Paper will be very opaque to UV light causing potentially extreme exposures. You should plan on using some kind of transparency material.

You will need to develop a process adjustment curve to allow proper rendering of tonal relationships when printing with digital negatives.


6) my printer ruins the surface during the printing

What kind of printer are you using?

There is a lot more we could address here but this should get the discussion going.

Don Bryant

[Don Bryant]

you need to do a step wedge to determine exposure times

Printing a step wedge will tell you what the basic coated paper speed is but you will need to allow for the density of base of the digital negative substrate to determine the minimum exposure time.

You can do this by covering half of the step wedge with the substrate and printing until the density of the first step of the covered part of the step wedge matches the DMAX of the uncovered step wedge.

there are several methods that can be used to increase contrast, the one that works best for our classes is to place about 10 drops of 10% solution of potassium dicromatic in a tray with about 2 liters of water before washing .

I've never gotten potassium dichromate to affect contrast but I've only used 5%, I'll have to try the 10%.

Which other methods have you used to increase contrast?

Don

[ann]

just dawned on me, that should be about 10 drops to 500 ml of water, sorry, tired brain tonight lol

don, we tried various amounts of the 10% solution to the sensitizing solution but not with much success, however adding to the first wash bath was successful

the dmax of the weston paper is also better, at least with my negatives and in my envrironment.

[Don Bryant]

just dawned on me, that should be about 10 drops to 500 ml of water, sorry, tired brain tonight lol

don, we tried various amounts of the 10% solution to the sensitizing solution but not with much success, however adding to the first wash bath was successful

Okay I'll try that.

Don

[Dan Williams]

g'day all
i've been experimenting with VDB and cyanotype printing using inkjet negs

i have encountered several problems, OHP materials are expensive, not readily available and my printer ruins the surface during the printing

so, paper negs -
are they viable?

can i somehow reduce the extremely long exposure times? (3 hours for the attached image)

ideas?

suggestions?

the attached image was originally captured with a 10Mp Canon 400D digital SLR, the file was converted to B&W and adjusted using a simple curve in PS8 then output to a thin coated inkjet paper which was then contact printed to VDB on gelatin sized paper

re VDB-
size or not?

one or two coats of emulsion?

how determine enough exposure?

what causes bronzing?

how increase contrast?

Not to make light of it but you have quite a list of problems here and not enough specifics to answer all your questions.

Paper negs are viable. You might want to do a Google search to find more information about them. I have made pinhole negs on paper that I then printed to VDB. I have not printed digital to paper and printed though. A couple of things to keep in mind. Some papers have very low UV transmission and VDB is a UV process. You can increase the transparancy of paper with various coatings, waxes, oils, etc. - I have done this for silver prints but not for any UV process so I don't know if it helps. I have read that it works for gum printers, another UV process, so I expect it will for VDB.

Two things about your printer -- You didn't say what you are using but some printers do mark OHP materials and, depending on the printer, there may de work arounds for the problem. The second thing is that some ink sets have low UV transmission and the choice of black or color ink printing can also influence the way your neg will print. There is a lot of information on this online.

You didn't mention what your light source is. It would help to know.

Three hours is an incredably long printing time. I print in a homemade 7 BL tube light box and I think the longest I have ever printed a dense camera neg was about 20 minutes. My digital negs print quicker than that.

I do double coat - It helps with D-max but, since most of my camera negs don't have the density required for VDB, I usually scan them and make digital negs for VDB. Once you get a good curve for them, it goes pretty smoothly. If you haven't run across PDN or Charthrob, do a search for them.

There are a number of things that can cause bronzing. One of them is over exposure. With a 3 hour exposure, this may well be your problem.

As to contrast, with a digital neg you control it with the curve you apply.

Dan

[Ray Heath]

g'day all
great info, i need to re-read and consider it all, thank you

another question re: VDB - i'm having problems being sure that the emulsion is dry enough, some advise printing bone dry, some advise printing when very slightly damp, i've already ruined 2 LF negs to 'very slightly damp', which seemed to not give any better result (just the ruin of 2 negs)

so - can VDB coating be dried with warm air?

thnx
Ray

[ann]

printing damp, surely someone is kidding.

you can dry the coating with warm air. we let the paper begin to dry on it's own and then finish it in a film dryer at a very low temperature.

you could use a hair dryer but dry from the back side of the paper (non coated side).

i missed something , a 3 hour exposure. oops just went back to re-read and discovered your point about that length of expsoure,

expsoure in our sitituation runs for 8 to 30 minutes, using a UV book.

[Don Bryant]

g'day all
great info, i need to re-read and consider it all, thank you

another question re: VDB - i'm having problems being sure that the emulsion is dry enough, some advise printing bone dry, some advise printing when very slightly damp, i've already ruined 2 LF negs to 'very slightly damp', which seemed to not give any better result (just the ruin of 2 negs)

so - can VDB coating be dried with warm air?

thnx
Ray

Ray,

Damp is not good. You can allow the paper to air dry with a fan blowing on it. Low heat with a hair dryer will also work, just don't over do the heat.

Don