Fortunately, you don’t need any photographic developer or other chemicals. You just need ammonia and a good development container.

Ammonia: Ammonia fumes are used to develop the paper. Just put the exposed paper in the presence of ammonia fumes and the paper will start to turn blue and white rather than yellow and grayish. My favorite method of development is to pour about a cup of generic ammonia from the grocery store into a small cup, then place the cup in the bottom of a large sealable bucket.

If you find that you need more fumes than you are currently getting, try heating the ammonia. I have had luck with microwaving a glass jar of ammonia and placing the pan on top of a hotpad in the bucket. Also, you can always just heat a nail or other piece of metal using a candle and drop the metal into the ammonia. Just be sure to cover the top with plastic wrap while it’s heating, and be very careful when removing the plastic. I haven’t experienced much steam, but I the fumes are especially strong.

However you use it, be sure that your development container is sealed; the fumes can be overwhelming and potentially dangerous.

Bucket: Any large and clean bucket with a lid will do. As long as the exposed paper can fit inside the bucket without overlapping, the bucket is large enough. I have used several types of buckets, boxes, crockery, tubs, and even a garbage bag. A bucket is by far the easiest. If you get one with a handle, it’s also portable!

If you need to develop large sheets of paper and you do not have a sealable container large enough to hold the sheet, you can loosely roll the sheet and stick it into a bucket. Put the ammonia container in the middle of the bucket, and pull a garbage bag over the paper and bucket, keeping in the ammonia. If you heat the ammonia first, even 18×36 sheets can be developed quickly using this method. Processing blueprint paper is very simple. No stop baths, no fixer, just ammonia fumes. Once the paper is exposed to ammonia fumes, it will begin to turn blue, revealing your print.

Time: I generally give a small print 3 minutes to develop, which is probably a bit long. I don’t think overdeveloping is a big problem with blueprint paper. I have overdeveloped a sheet before, but the blue was fine. The rest of the paper turned an odd brown. However, it was exposed to ammonia for several days.

Alternative method: Mary McCabe sent this alternative processing method to the mailing list: After putting in the sun as I described, I wash it for a minute to 1.5 minutes in plain water in a tub. Then in the next tub I’ve prepared plain water with the hydrogen peroxide added. I wash it for no more than a minute, usually less. The paper turns a lovely dark blue to lighter blue depending on what the transparency has on it. What I generally do is fill that tub, put in some hyd. per. and use a test small piece I’ve had in the sun for a minute or 2 until it turned white. This tests the amount of hyd. peroxide that I have in. Just get a bottle from Target (I guess some people use it on their hair or to lighten mustache hair around their lips. ). How did I find out about this? The art people at UT-Austin had a workshop a few months ago that I went to and they told us about the h.p.