The prin­ci­ple behind Day Glo ink is both sim­ple and mind-blow­ing. When we see a colour on a page, this is the nat­ur­al light being trans­formed and reflect­ed back off the colour to our eyes. Day Glo pig­ments not only reflect this light back, but the also pig­ments con­vert some of the unseen light — ultra­vi­o­let light — to vis­i­ble light. When this reflects back to our eyes we per­ceive that more light is reach­ing our eyes than in the wider envi­ron­ment — look­ing like the colours are them­selves glow­ing or giv­ing off their own light.

The Day-Glo Col­or Corp. was found­ed in Ohio in 1946 by Joseph and Robert Switzer, but the broth­ers had been work­ing on pig­ments with these qual­i­ties since the 1930s.

By Novem­ber 1950, the British Print­er ran a detailed arti­cle on the cur­rent state of Day Glo in the UK. The pig­ment was ini­tial­ly only offered to hand-painters (for signs) and screen print­ers. There was some relief that all man­ner of print­ing could­n’t use Day Glo inks and that it would be lim­it­ed to some spe­cif­ic uses. While best in day­light — con­tain­ing the ultra­vi­o­let light need­ed for con­ver­sion — the arti­cle notes that posters that were ​‘invis­i­ble’ beyond 50 yards remained clear­ly vis­i­ble at 200 yards when print­ed Day Glo.

The ini­tial appli­ca­tion of Day Glo had to be in a film ³/₁₀₀₀th of an inch thick mean­ing it could not be applied through let­ter­press which lays a film much thin­ner than this. Ini­tial colours were the now-famil­iar crim­son, ver­mil­lion, green and yel­low but to give an impres­sion of their bril­liance these were re-named — Neon Red, Fire Orange, Sat­urn Green and Sig­nal yel­low. Day Glo posters were list­ed as hav­ing around a month of fade resis­tance in strong sun­light.

Just as have many oth­er spec­tac­u­lar inno­va­tions, so has ​‘Day Glo’ suf­fered from mis­use in its ear­ly days. Hoard­ings in the vicin­i­ty of The Hay­mar­ket and Leices­ter Square have been plas­tered with such unre­strained enthu­si­asm that they have become caul­drons of riotous colour: super­flu­ous bril­liance so engulfs the pass­er-by that he can­not pos­si­bly, with­out dif­fi­cul­ty, assim­i­late any­thing but the largest pat­terns and let­ters.

– British Print­er com­ment on Day Glo, Novem­ber — Decem­ber 1950

The next devel­op­ment to bring us let­ter­press Day Glo was a change of approach by 1957 where a Chica­go print­er was not­ed as using litho but then a bronz­ing-type process to apply Day Glo pig­ments. Essen­tial­ly, slight­ly wet ink is dust­ed with Day Glo pow­der, and a light brush dusts away the pow­der from the non-stick­y/uninked areas of the paper. This pow­der was not as light fast as the inks used in screen print­ing.

Day Glo Letterpress

https://www.tumblr.com/thesalvagepress/41516984606/the-first-colour-on-this-poster-is-a-flouro

By 1962, Dane & Co inkmak­er was offer­ing Day Glo let­ter­press inks. They had been offered ear­li­er but had to be applied in two coats. The inks dried with­in 4–6 hours and were as light-fast as the screen inked ver­sions.

Day Glo then became anoth­er char­ac­ter­is­tic of let­ter­press that can’t be eas­i­ly repli­cat­ed at home. We can each now print high qual­i­ty pages, with many dif­fer­ent fonts from our own home, but like the light impres­sion of let­ter­press, it’s not easy to recre­ate Day Glo at home.

Suppliers Today

My favourite let­ter­press ink sup­pli­ers each offer flouro inks:

Day Glo and Paper

One addi­tion­al Day Glo inno­va­tion made it in to the world of com­mer­cial print­ing — just as the base chem­i­cals behind Day Glo reflect back addi­tion­al vis­i­ble light, paper­mak­ers could add a small amount of ​‘opti­cal white’ pig­ments to their papers.

By adding just 0·05% of phos­pho­res­cent zinc sul­phide to dry pulp, the result­ing paper reflects back more vis­i­ble light giv­ing the over­all effect of an ultra-white stock.

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Location

Cleve­land, Ohio as head­quar­ters of the Day Glo Corp.

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Head­er Image: ​“An ear­ly Globe Poster” flickr pho­to by Nick Sher­man https://flickr.com/photos/nicksherman/14992854186 shared under a Cre­ative Com­mons (BY-NC-SA) license