I've always been fascinated by autochromes.  If you've spent any appreciable amount of time here on this site, you'll also notice that I am fascinated by photographic processes that one can make entirely from scratch.  Especially positive processes.  Early on in my journey to make my own color photographs, there seemed to be two feasible processes: autochromes and Lippmann plates.  I was intrigued, because both of these processes are actually based around a black and white silver gelatin emulsion!  However, the way they produce their color vary in wildly different ways.

 

Autochromes are an additive color process -- meaning that they use a mixture of red, green and blue light to create a wide range of colors to our eyes.  They are viewed by transmitted light, meaning the final product is a positive color 'slide'.  In accordance with the laws laid out by James Clerk Maxwell's Color Theory, it is our eyes and brain that interpret different ratios of red/green/blue light as a wide range of colors.  The same principles are applied constantly in color reproduction, including the very monitor you're reading this article on!

 

To dive in a little more closely, there are two major portions of the complete autochrome plate - the 'screen' and the emulsion.  The autochrome screen consists of glass, with a layer of potato starch dusted on one side.  The starch is a mixture of red-orange, green and violet grains.  When mixed together, they form a sort of neutral dark color, and when applied to glass, the light transmitted is a neutral light gray.  The starch is compressed to increase the amount of light transmitted, and covered with a protective layer of varnish, which prevents the starch from coming into contact with the chemistry during processing. 

 

The emulsion is the photosensitive portion of the plate -- a simple panchromatic black and white emulsion is laid on top of the screen.  The emulsion acts as a filter, blocking certain colors of starch grains and allowing light through in others.  This is how we get our color reproduction. 

 

I've spent a lot of time researching and planning out how to make autochromes of my own.  It's difficult, but not impossible.  I've currently had some solid successes, but there's quite a bit more to learn and re-discover about the process.  I'm hoping what I've outlined here encourages other adventurous experimenters to try making autochromes for themselves.

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I've spent a lot of time researching and planning out how to make autochromes of my own.  It's difficult, but not impossible.  I've currently had some solid successes, but there's quite a bit more to learn and re-discover about the process.  I'm hoping what I've outlined here encourages other adventurous experimenters to try making autochromes for themselves.

Part 1  - Mixing the Second Varnish

Autochromes require of two specific varnishes - coined by the Lumières as 'first' and 'second' varnishes.  The first varnish is an optically clear, rubber-based tacky varnish that holds the starch grains in place.  The second varnish acts as a protective barrier, keeping the various processing chemicals from disrupting the starch and causing dye bleeding.  The second varnish needs to be mixed first, as some insoluble damar gum residue is used as an ingredient for the first varnish. 

Collect the following ingredients:

  • 300mL Ethyl Acetate

  • 28.8g Damar Gum

  • 38.7g nitrocellulose lacquer

  • 4.5g castor oil

The ethyl acetate was source off of Amazon.com and the damar gum sourced from Etsy.  The original Lumière recipe called for raw nitrocellulose, rather than the nitrocellulose lacquer.  Currently, I have not been able to replicate the original formula as it was.  When adding in nitrocellulose (sourced from a magic supply store as flash cotton), it causes the mixture to turn thick and gelatinous.  Even with the addition of 600mL ethyl acetate, I could not get this to act as a usable varnish.  A portion of the lacquer had been weighed and allowed to dry, calculating approximately how much of the weight content was nitrocellulose.  This allowed us to extrapolate that 38.7g of Behlen nitrocellulose lacquer will deliver us our required 7.2g nitrocellulose.  The inclusion of castor oil did not seem to affect the varnish's behavior noticeably.

Add the ethyl acetate, damar gum and nitrocellulose lacquer to a 500mL beaker, and add a magnetic stir-bar if you have a magnetic mixer.  Ethyl acetate is extremely volatile, so make sure this is all done outside or under a properly rated fume hood.  Cover the beaker with beaker with saran wrap (or some other plastic) to prevent unnecessary evaporation.  Allow this mixture to sit for 24 - 48 hours, until the damar gum crystals have broken down, leaving behind a white powdery residue.  I prefer to run the mixer for a minute every couple of hours to facilitate the dissolution.  Be careful not to run the mixer constantly; the insoluble portion will break down into particles so fine that even my smallest filters were ineffective, and it will take weeks for them to re-congeal to a filterable state. 

Filter the solution (coffee filters seem fine) and save the residue.  Bottle and label the solution. 

Add the

Part 1  - Mixing the Second Varnish

Autochromes require of two specific varnishes - coined by the Lumières as 'first' and 'second' varnishes.  The first varnish is an optically clear, rubber-based tacky varnish that holds the starch grains in place.  The second varnish acts as a protective barrier, keeping the various processing chemicals from disrupting the starch and causing dye bleeding.  The second varnish needs to be mixed first, as some insoluble damar gum residue is used as an ingredient for the first varnish. 

Collect the following ingredients:

  • 300mL Ethyl Acetate

  • 28.8g Damar Gum

  • 38.7g nitrocellulose lacquer

  • 4.5g castor oil

The ethyl acetate was source off of Amazon.com and the damar gum sourced from Etsy.  The original Lumière recipe called for raw nitrocellulose, rather than the nitrocellulose lacquer.  Currently, I have not been able to replicate the original formula as it was.  When adding in nitrocellulose (sourced from a magic supply store as flash cotton), it causes the mixture to turn thick and gelatinous.  Even with the addition of 600mL ethyl acetate, I could not get this to act as a usable varnish.  A portion of the lacquer had been weighed and allowed to dry, calculating approximately how much of the weight content was nitrocellulose.  This allowed us to extrapolate that 38.7g of Behlen nitrocellulose lacquer will deliver us our required 7.2g nitrocellulose.  The inclusion of castor oil did not seem to affect the varnish's behavior noticeably.

Add the ethyl acetate, damar gum and nitrocellulose lacquer to a 500mL beaker, and add a magnetic stir-bar if you have a magnetic mixer.  Ethyl acetate is extremely volatile, so make sure this is all done outside or under a properly rated fume hood.  Cover the beaker with beaker with saran wrap (or some other plastic) to prevent unnecessary evaporation.  Allow this mixture to sit for 24 - 48 hours, until the damar gum crystals have broken down, leaving behind a white powdery residue.  I prefer to run the mixer for a minute every couple of hours to facilitate the dissolution.  Be careful not to run the mixer constantly; the insoluble portion will break down into particles so fine that even my smallest filters were ineffective, and it will take weeks for them to re-congeal to a filterable state. 

Filter the solution (coffee filters seem fine) and save the residue.  Bottle and label the solution. 

Add the

Part 2  - Mixing the First Varnish

As stated before, the objective of the first varnish to provide a clear, sticky coating to the glass, to hold the starch in place.  This varnish doesn't deviate much from the original Lumière recipe, simply latex from common rubber cement, rather than the raw material itself.

  • 87mL Toluene

  • 13.3g Rubber Cement

  • ~6mL 10% solution of previously insoluble damar residue, dissolved in toluene.

The 13.3g of Elmer's brand rubber cement correlates roughly to 1.5g latex when dry.  Xylene, which is more easily sourced locally (for me, at least) seems to perform just about as well as toluene.  Due to the toxic nature of the fumes from these chemicals, all work with this varnish should be done under a fume hood or outside. 

Part 3  - Dyeing the Starch

This is probably the messiest step of the process.  Working with pure dyes should be done in a sink, as they can and will get everywhere (particularly crystal violet).  Proper PPE should be worn here - goggles, gloves, labcoat and dust mask.  Regardless of how slowly the powders are handled, dust-maskless mixing will inevitably result in one's snot being dyed a variety of colors. 

Sourcing

Some of the dyes can be tricky to track down.  Here's a list of dyes, alternate names, and links to where I was able to find them.
 

Additionally, the green dye procedure calls for concentrated ammonia hydroxide and sodium sulfate.  A magnetic mixer, 50mL beaker and vacuum filtration setup will be pretty much necessary for all the following steps.  Currently, I use "Bob's Red Mill" potato starch, though I suspect that most kinds should work fine.  Right now I do not sort the starch, which results in a very grainy final product. 

Orange Grains

In a 50mL beaker, add:

  • 3.75g Erythrosine

  • 0.665g Rose Bengal

  • 5g Tartrazine

  • 15g Potato Starch

  • 15mL Water

Stir magnetically for one hour.  Vacuum filter off the excess dye solution, and add the powder to 200mL 1:3 water to alcohol solution.  Stir magnetically for a few minutes, then vacuum filter again.  Allow starch to dry thoroughly.

Violet Grains

In a 50mL beaker, add:

  • 2.15g Crystal Violet

  • 0.3g Malachite Green

  • 15g Potato Starch

  • 30mL Water

Stir magnetically for one hour at 30C.  Vacuum filter off the excess dye solution, and add the powder to 200mL 1:3 water to alcohol solution.  Stir magnetically for a few minutes, then vacuum filter again.  Allow starch to dry thoroughly.

Green Grains

In a 50mL beaker, add:

  • 4.6g Tartrazine

  • 2.2g Patent Blue

  • 4.6g Sodium Sulfate

  • 15g Potato Starch

  • 25mL Water

  • 2g Ammonia Hydroxide

Stir magnetically for one hour.  Vacuum filter off the excess dye solution, and add the powder to 200mL 1:3 water to alcohol solution.  Stir magnetically for a few minutes, then vacuum filter again.  Allow starch to dry thoroughly.

Mixing the Starch

Getting a properly neutral mix can only really be determined experimentally.  Equal portions of the starches do not equal neutral color.  Currently, my ratio is 5g Red : 6g Green : 5g Violet : 3g Blue.  Blue here is a failed run of violet grains that I washed too much, removing a good portion of the crystal violet.  This hopefully gives you a starting point, though ultimately the final ratios will depend on how the starches turned out.  The powder should take on a very dark color, tinted slightly red.

Part 4  - Dusting the Starch

As stated before, the objective of the first varnish is to hold the starch in place on the plate.  To prepare the plate for this, I like to line the outside of the glass with masking tape, forming an 1/8" border around the edges.  The first varnish is flowed on the plate "collodion style" - gently rocking the plate allowing the varnish to contact the entirety of the surface.  A corner is tipped back into the bottle containing the varnish, allowing the excess to drain.  The plate is allowed to sit on a level surface to dry.  If done correctly, once all solvent has evaporated, the varnish should be fairly sticky to the touch.  After drying, the masking tape can be removed. 

A quantity of the mixed starch can be placed on the plate, and the pile gently spread around with a soft brush until starch has contacted the entirety of the tacky area.  Gently return excess starch back into the container with the brush.  Repeat this step with charcoal, which will be used to fill in the interstitial
spaces between the starch grains.

Finally, a similar quantity of talc should be added to the plate and brushed around, gently, in the same manner as the starch and charcoal.  The talc will take on a grey color as it mixes with excess charcoal.  Dispose of the excess talc, and gently brush the plate while blowing to remove most of the remaining talc.