thomastelford

article on the process of photochrom: en.wikipedia.org/wiki/Photochrom "A litho stone is coated with a thin layer of purified bitumen dissolved in benzene. A reversed half-tone negative is then pressed against this light-sensitive coating and an exposure in daylight made (taking from 10–30 minutes in summer, to several hours in winter). The bitumen hardens and becomes resistant to normal solvents in proportion to the light. The coating is then washed in turpentine solutions, removing the unhardened bitumen. It is then retouched in the tonal scale of the chosen color to strengthen or soften the tones as required. Each tint needs a separate stone bearing the appropriate retouched image, and prints are usually produced by at least six, and more commonly from 10 to 15 tint stones.[4]"

article on the process of photochrom: en.wikipedia.org/wiki/Photochrom "A litho stone is coated with a thin layer of purified bitumen dissolved in benzene. A reversed half-tone negative is then pressed against this light-sensitive coating and an exposure in daylight made (taking from 10–30 minutes in summer, to several hours in winter). The bitumen hardens and becomes resistant to normal solvents in proportion to the light. The coating is then washed in turpentine solutions, removing the unhardened bitumen. It is then retouched in the tonal scale of the chosen color to strengthen or soften the tones as required. Each tint needs a separate stone bearing the appropriate retouched image, and prints are usually produced by at least six, and more commonly from 10 to 15 tint stones.[4]"

Correct spelling is Pontcysyllte. (Now a World Heritage Site) en.wikipedia.org/wiki/Pontcysyllte_Aqueduct

hefhoover: Thanks for pointing out the correct spelling. We'll fix the description next time we update.

No problem, thanks for posting these superb photographs. :-)

The aqueduct today. www.flickr.com/photos/speedtree/3488388724/

See view of bridge from a distance as a photochrom from the Library of Congress. The Telford suspension bridge is at far left. Comments include a current Street View.

It looks quite a bit different nowadays. www.flickr.com/photos/roger_forster/46076168251/in/album-...

article on the process of photochrom: en.wikipedia.org/wiki/Photochrom "A litho stone is coated with a thin layer of purified bitumen dissolved in benzene. A reversed half-tone negative is then pressed against this light-sensitive coating and an exposure in daylight made (taking from 10–30 minutes in summer, to several hours in winter). The bitumen hardens and becomes resistant to normal solvents in proportion to the light. The coating is then washed in turpentine solutions, removing the unhardened bitumen. It is then retouched in the tonal scale of the chosen color to strengthen or soften the tones as required. Each tint needs a separate stone bearing the appropriate retouched image, and prints are usually produced by at least six, and more commonly from 10 to 15 tint stones.[4]"

Title should read, from The Marquis of Anglesey's column. It's a magnificent structure, but getting a little delapidated internally now, with many steps in ned of repair. Link to a 360 deg view, showing how the area has changed. www.northwalesattractions.co.uk/Images/Virtual/MofA/MofAC...

Streetview