It is quite common to have undeveloped patch on your Polaroid / Impossible films. No matter you are taking photos with SX-70, 680 or 690 camera, you may have experienced undeveloped patch. It could be due to dried chemical, or uneven roller pressure. This is fairly normal.
Why three chemical patches?
It is because the Impossible film is vertically divided by three parts. When you take pictures with SX-70, two rollers push the chemicals out of the pouches, and let the chemicals to be evenly distributed on the image. Therefore, if the undeveloped patch is located at the centre of film, probably it means there is a problem on the middle chemical pack.
The earliest film from Impossible
The film production technique was not as mature as today’s, so problems arose. For example, PX70 First flush film was much likely to have undeveloped patch than the Impossible’s latest Color 600, White Frame 3.0.
We recommend choosing films in a later phase like Color protection film and B&W 2.0. They have less chance to have undeveloped patch.
If you place your films in a hot, humid place or even under sunlight, an unfavourable chemical reaction may result and lead to agglomeration of chemical. The rollers may not smoothly push the chemicals out and thus affecting the result image.
Aside from the storage of film, there is also a possibility of splotchy rollers or damage of rollers that the chemicals could not be pushed out and distributed evenly on the picture.
You can gently hold the film door (but don’t block the picture exit slot under front edge) when taking picture.
Clean the rollers
Change Polaroid 680 / 690 rollers to new ones
Cleanliness of the rollers is utterly important. But there is one more thing, Dr. Love from The Impossible Project states that
“For any of you who happen to own an SLR 680, you know it is a beautifully well-crafted work of art of instant electronic machinery….it also tends to produce more ‘divots’ or [‘undeveloped patches’] than your friend’s SX-70 camera.
You may be wondering…why?
The simple answer here is the one thing in the ejection process that changes from the older SX-70 cameras to the SLR 680 and 690 model folding cameras, that is the rollers.
The roller set on these cameras are a little different than the ones found on the SX-70s. The rollers were changed to improve durability and grip on the film, but in the case of newer, more sensitive Impossible films, sometimes there is a less perfect spread of developer leaving the gap of paste at the top of the frame.”
Read more: http://bit.ly/VObMfv
So we highly recommend you to change the old rollers on Polaroid 680 / 690 to achieve the best performance!