array(1) {
[0]=>
array(41) {
["_id"]=>
string(10) "collotypes"
["_enhanced_status"]=>
string(0) ""
["_abbrev"]=>
string(2) "CO"
["_name"]=>
string(10) "Collotypes"
["_synonyms"]=>
string(0) ""
["_use_term"]=>
string(0) ""
["_popular_start_date"]=>
string(4) "1873"
["_popular_end_date"]=>
string(4) "1895"
["_aat_id"]=>
string(9) "300154355"
["_aat_level_1"]=>
string(35) "visual works by medium or technique"
["_aat_level_2"]=>
string(22) "photomechanical prints"
["_aat_level_3"]=>
string(16) "photolithographs"
["_aat_level_4"]=>
string(0) ""
["_aat_level_5"]=>
string(0) ""
["_aat_level_6"]=>
string(0) ""
["_aat_level_7"]=>
string(0) ""
["_searchkey"]=>
string(0) ""
["_filename"]=>
string(0) ""
["_type"]=>
string(0) ""
["_base"]=>
string(0) ""
["_dates"]=>
string(0) ""
["_alternative"]=>
string(0) ""
["_edinburgh"]=>
string(0) ""
["_leggat"]=>
string(0) ""
["_0896594386"]=>
string(0) ""
["_VA"]=>
string(5) "pr015"
["_christies"]=>
string(0) ""
["_britishlibrary"]=>
string(0) ""
["_private_notes"]=>
string(1358) "Collotype
A photo-lithographic process that produces prints in ink from a photographic image made of gelatin. Like carbon (see above) and gum-bicromate (see below) printing, the collotype process is based on the light sensitivity of dicromated colloids. When ammonium or potassium dichromate is dissolved in gelatin and allowed to dry, the mixture becomes light sensitive. Areas absorbed to light lose their ability to absorb water and thus contact exposure under a positive transparency hardens the gelatin in proportion to the amount of light falling upon it. When an exposed plate is washed in water, blotted, and then rolled up with greasy ink, the plate takes up more ink where the exposure to light was greatest. This inked matrix is printed onto paper on a lithographic press. Under magnification, collotype images have a characteristic reticulated pattern from the gelatin surface.
The first successful collotypes were made by Alphonse Poitevin in 1855 using a lithographic stone coated with bicromated gelatin, a process he called "photolithographie". Various improvements quickly followed and by the 1870’s there were a remarkable number of collotype processes, each with its own name: Albertype, atrotype, autogravure, autotype, heliotype, lichtdruck, photocollographie, photogelatin, phototypie, phototype, and phototint. (Joseph Bellows)"
["_notes_discovery"]=>
string(0) ""
["_notes_technical_details"]=>
string(0) ""
["_notes_preservation"]=>
string(0) ""
["_notes_summary"]=>
string(0) ""
["_notes_photographers_of_note"]=>
string(0) ""
["_notes_current_use"]=>
string(0) ""
["_notes_identification"]=>
string(0) ""
["_notes_possible_confusion"]=>
string(0) ""
["_notes_thanks"]=>
string(0) ""
["_exhibition"]=>
string(0) ""
["_catcode"]=>
string(3) "763"
["_image_ids"]=>
string(0) ""
}
}
