This is a brief report on a quick test I did comparing three different batches of DAS sensitizer for carbon transfer printing. Plain and simple – have a look at the outcome.
The background to this is that Charles from Secant Chemicals contacted me with the question whether the DAS I bought from him some time ago actually works for carbon transfer. The context was a question of another customer of his and he just wanted to verify nothing odd was going on with the batch of chemistry he also supplied to me. I hadn’t actually gotten round to trying his DAS out yet, but it was easy enough to give it a try.
I cooked up some carbon tissue with DAS from three different sources I have on hand. The tissue formulation was as follows:
- Gelatin: 11% w/v of the total glop volume
- Sugar: 50% w/w of the gelatin weight
- Kremer XSL black pigment: 1.6% w/w of gelatin
- DAS: 4% w/w of gelatin
This is a tissue formulation that I have found to work well for me as a ‘general purpose’ tissue of moderately high contrast, but still capable of decent highlights.
The DAS I used came from three different sources:
- Secant Chemicals / Charles Scanio (cjscanio [at] yahoo [dot] com). This is a brick-red powder with some lumps, which dissolves to make an orange solution with a tiny bit of sedimentation that can mostly be broken up by crushing the tiny chunks with a stirring rod.
- Interchema / Antonides. This material looks identical to the Secant DAS. I have it on good authority that it actually is the same stuff.
- The Wet Print / Calvin Grier. This DAS looks much different and is a lighter, more fluffy powder with no lumps; the color is pale creme. It dissolves without any residue to make a pale light solution.
Not tested, but as far as I can tell identical to the Secant and Antonides DAS is the DAS I’ve used from Phototypie.fr. However, this has been sold out or no longer listed lately. I strongly suspect this material also came from Secant.
Here’s the print I made; shown is the one made with the Secant DAS:
Exposures were (of course) identical and I used two separate exposures for each print, first an exposure for the shadow density using 395nm COB LED followed by a 365nm COB LED exposure for the highlights. The exposure time for the 395nm exposure was about 3x that of the 365nm exposure; both COB LEDs are 100W nominal. I used my recently revamped UV integrator to get consistent exposures.
Since I included a Stouffer T2115 in the print, I could measure the densities quite easily. I did not transfer the prints to a final support and instead simply measured the densities off of the print on its temporary support. This removes any influence of the final support paper, but may introduce slight variations due to diffusion of light in the transparent film base. Because this will be identical for all three prints, I don’t consider it an issue. Clear Yupo was used as a base, ensuring a decently clear minimum density (white).
The measured curves end up plotting like this:
Note how the Secant DAS and the Wet Print DAS print virtually identically. The Interchema/Antonides curve lags a little. There can be various explanations for this, including measurement inaccuracies on my end. I made three small batches of glop for these tests and this brings the inherent possibility of minor inconsistencies. It’s also conceivable that the Antonides DAS was of an older batch than the otherwise identical Secant material, and that aging plays a role. However, I’m skeptical of this, since the color of the powder is exactly the same, and DAS turns very dark as it breaks down, so I’d expect to see a distinct color difference. Ultimately, the difference between the curves is kind of small; the dmax for the Antonides DAS works out as ca. 1.80 while the Secant and Wet Print top out at 1.88-1.89.
This was sufficient to answer Charles’ question – the batch of DAS he has been selling works as one might expect for carbon transfer.
For more firm conclusions as to the relative differences, much more tightly controlled testing would be necessary. Presently, I have no reason to conduct such tests, so I’m going to leave it at this quick assay.