Impossible · ISO 100 B&W negative
Impossible PX 100
PX 100 was the first instant film the Impossible Project shipped, released on March 22, 2010, eighteen months after the team took over the last Polaroid factory in Enschede and rebuilt integral chemistry from scratch. The stock is for SX-70 cameras at ISO 100. The launch carried the name Silver Shade First Flush, an admission the chemistry was still in development.
What the First Flush produced was not a true black-and-white image. Tones drifted toward sepia, the opacifier layer was not fully light-tight, and you had to shield prints on ejection or watch them bleach out. Development ran about three minutes face-down in darkness near 21 C. Cooler temperatures pulled toward neutral grey; warmer temperatures pushed further into yellow.
Ilford Photo helped Impossible launch PX 100 and the companion PX 600 for 600 cameras, which places PX 100 closer to a silver-halide pictorial film than to legacy Polacolor B&W. Later iterations cleaned up the problems. The UV+ variant added a blocking layer to stop prints from continuing to expose during development; the Cool variant pulled tonal balance toward neutral monochrome. By 2013 the First Flush formulation was retired and the Silver Shade line carried forward under refined chemistry, eventually becoming current Polaroid B&W SX-70.
Compared with conventional Polaroid 600 B&W from its final production years, PX 100 ran more atmospheric and less neutral. Against current Polaroid B&W SX-70 film, the First Flush era reads more sepia and unstable. That instability is the point for some shooters.
Format is the SX-70 integral pack, eight exposures. First Flush stock is long out of production; later Silver Shade variants are also superseded. Current Polaroid B&W SX-70 is the direct descendant.
Reciprocity exponent is 1.0. Zone Light Meter applies the calculation past one second, but SX-70 cameras manage their own shutter and there is little room to push past that. A metered 2-second exposure stays at roughly 2 seconds. Temperature matters more than reciprocity ever does.
How the app handles this stock
- Box speed: ISO 100. Picker exposes pull/push chips so you can shoot it at any speed you want and the meter follows.
- Reciprocity: No reciprocity correction needed; metered time is the shot time.
- Expired film: if you load an old roll, set the expiry year and storage in the app and the ISO scales for you. B&W negative decay rates are baked in.