Signs for Designs Trivia Quiz

Answer: Cyanotype

The cyanotype process involves a chemical reaction that produces a print that is cyan (a shade of blue) in color. It was first developed by the English scientist Sir John Herschel in 1842. Another process used in making blueprints was that developed by Louis Poitevin in 1862, which used slightly different chemicals to produce similar results to those of the cyanotype process.

Blueprints using a cyanotype process are actually rarely used these days, as other technologies have replaced them, but architectural plans are often still called blueprints in common usage.

The image accompanying this question is an example of a cyanotype image produced in 1842 by Sir John Herschel.

Answer: Prussian blue

Prussian blue is also called Berlin blue, Parisian blue, and Turnbull's blue. The formula given in the question is actually what is called an idealized formula - when the pigment is produced, it usually contains impurities from the chemical reactions that produce it. Their presence can lead to slight changes in the hue. The shade of blue is also affected by the size of the particles formed in the colloid (a suspension of particles in water).

The image accompanying this question shows a blueprint drawn in the 20th century for the galleon La Belle, used by La Salle in his explorations of the US. It was lost off the coast of Texas, and the wreckage discovered in 1995.

Answer: Reduction of iron

The prefix ferri- is used to describe an ion of iron with a charge of +3. In the reaction, the Fe3+ from the ferric ammonium nitrate is reduced (gains an electron) and has a charge of +2 (described with the prefix ferro-). The ferrous ions produced then combine with the ferricyanide ions from the potassium ferricyanide to produce ferroferricyanide, or Prussian blue.

The image accompanying this question is a standard architectural blueprint showing a number of elevations and architectural details for a two-story house.

Answer: Glass

Glass is not porous, so it will not absorb the chemical mixture. It is possible to use glass (if you really want to) by coating the glass with a material such as gelatine which will absorb the chemicals, and fix them in place when it sets. Architects usually used paper, as you may recall from seeing the rolled-up paper cylinders that can be dramatically unrolled to reveal the plans. Artists applying the process to produce images of more aesthetic value have explored a range of other absorbent materials.

The image accompanying this question shows the Library of Congress under construction in 1893.

Answer: Expose it to sunlight

The UV portion of the sunlight is actually the essential component, as it provides the energy to reduce the iron ions, so you can also use a UV light source if sunlight is an issue. Those portions of the surface which the UV light affects will turn blue; those parts that are blocked (because of being dark areas in the negative placed on top) will not change color, and will appear as light areas in the final print. A typical blueprint exposure time would be between five and twenty minutes. Architectural drawings to be turned into blueprints are drawn on translucent paper, so that only the areas where the lines for the plan are drawn will block the sun. If you have placed an ordinary object, such as a flower, on the surface instead of a drawing, you will produce a photogram, a negative image of the original object.

The image accompanying this question, titled 'Carix (America)', was made by Anna Atkins, an English botanist who published a book, 'Photographs of British Algae: Cyanotype Impressions' (1843), using the technique invented by her friend John Herschel, which is considered the first book with photographic illustrations. They were created by placing the plant specimen on the photosensitive surface, and creating a photogram.

Answer: Developing

The same term is used for other photographic processes to describe the stage in which the photosensitivity of the materials is removed. In the case of blueprints, the unused chemicals can be simply washed away with running water, since they are quite soluble, unlike the blue product. As the material dries, the blue color usually becomes slightly darker, so it takes some practice to know how dark is needs to be before ending exposure and stopping the process.

The image accompanying this question shows a sample of woodhorsetail, by Anna Atkins.

Answer: Sodium hydroxide

Sodium hydroxide is a strong base, not an acid or an oxidizing agent. Lemon juice contains citric acid, and vinegar contains acetic acid, both of which are weak acids. Hydrogen peroxide is an oxidizing agent. Oxidizing agents and acids reactivate the chemical process, and increase the speed of the reaction that forms the Prussian blue. This gives larger particles, which have a darker color. It is only limited in effect, however - it is better to get the exposure right the first time!

The image accompanying this question was taken by Anna Atkins, of the algae Dictyota dichotoma, showing several stages of development.

Answer: Washing soda

Chlorine bleach, washing soda (NOT baking soda), ammonia, borax, and a range of other chemicals can be used to reduce the color intensity in the finished blueprint. After exposure, the print is developed and thoroughly dried, then placed in a weak solution of the chosen chemical for a short time. It must then be rinsed thoroughly, or the bleaching process will continue. If an even lighter color is desired, the process can be repeated, but it is recommended that you let the print dry first (as the color intensity does change on drying) so you can see whether or not it is still too dark.

The image accompanying this question shows some fronds of the fern Pteris aquilina, an image created by Anna Atkins.

Answer: Coffee produces a blue-black color

All of these coloring agents contain tannin, which is the principle agent in changing the color of the iron compound. Red wine and black tea both produce a dark brown, almost black, color; green tea produces a dark purple-black color, similar to a ripe eggplant. The exact shades produced depend on the strength of the solution used, the length of time for which the print is soaked, and temperature. It is definitely more an art than a science!

The image accompanying the question was taken in 1895, and shows the last buildings left in the abandoned Zion Hill Mission in what is now Nundah, Queensland.

Answer: Store it in a completely dark environment until it looks good again

Cyanotype prints should be stored in the dark for ideal preservation. If you want to put them in an album, do not use one of the special acid-free paper albums recommended for photographs - cyanotypes do not react well to the basic environment in them. If you want to put a framed print on display (or if you have it printed onto clothing which you wear) and it is exposed to light, it will fade over time. However, this can be largely reversed simply by placing it in complete darkness and letting the Prussian blue re-create itself.

The image accompanying this question is one last contribution from Anna Atkins, titled 'Foreign Ferns' - no further details are available. If you are interested in her work, you can find more examples in Wikimedia Commons, in the Cyanotypes category.