The glorious sunshine has given me a chance to use the Fibrecrafts Cyanotype Blue Printing Kit. Include in the kit are enough chemicals to make up to 1 litre of solution, a 1/2 metre each of silk and cotton fabric, and a step-by-step instruction leaflet.
Cyanotype printing is a negative process – where light cannot reach the sensitised areas the colour does not develop. Items such as leaves, petals or feathers can be used as a mask, as can an acetate sheet with an image drawn on it in permanent ink, or large photographic negatives.
The chemical solution of the iron salts (ferric ammonium citrate and potassium ferricyanide) is sensitive to ultra violet (UV) light.
A substrate, such as paper or finely woven cotton or silk fabric, is coated with the solution and left to dry naturally in a dark room or cupboard. The dried coating turns to a greeny-yellow in colour. It will change colour to a greyish blue when exposed to direct sunlight or another UV light source.
When the print has fully exposed (times will vary depending on the intensity of UV light), the print is then rinsed in running water until the undeveloped chemical is removed. As the material dries, the print will oxidise and turn into the Prussian blue associated with the cyanotype blue printing process.
Cyanotype Print using Hand Drawn Stencil on Clear Acetate Film
The photograph below shows a print I made using an acetate sheet with a design drawn in black fibre-tip pen. To get a clear print it is necessary to keep the acetate sheet stencil as flat and close to the fabric as possible. Clear adhesive tape, the weight of a sheet of glass or empty picture frame can be used to help maintain contact with the surface. The less clear areas of my print (down the right hand side and bottom) are where my acetate sheet was slightly curled away from the fabric.
This print on silk fabric, below, was created using the same technique as above.
A close-up shows a number of things to watch out for! The contrast of the print is not brilliant and this is where the lightweight silk fabric was exposed to the light for a short time before placing my stencil over it, hence the pale blue sun which should have remained white. Below the image of the sun is an area that has not developed and this is probably where I did not cover the fabric evenly with the solution, or it may be where it made contact with another surface while drying which leached the wet solution away from the silk.
Cyanotype Print using Negative Image on Inkjet Printable Acetate Film
These final images show a cyanotype image using inkjet printable acetate film. The film negative image was created from a positive image in Adobe Photoshop. Remember to print the image in black ink. I made the mistake of printing it in full colour which resulted in a semi-opaque stencil . This produced a subtle effect caused by some of the UV light being able to transmit through the masked areas. 
I hope that my errors will help you to avoid making the same mistakes. The contents of the Fibrecrafts Cyanotype Blue Printing Kit provide you with enough chemicals to make 4 batches of 250ml – plenty for experimentation and a number of successful prints! ~ Allison Holland