Editing Shadow mask (section)

===Manufacture===
Shadow masks are made using a [[photochemical machining]] process. It starts out with a sheet of steel<ref>{{Cite web|url=https://patents.google.com/patent/US6094003A/en|title=Anti-doming composition for a shadow-mask and processes for preparing the same|access-date=5 December 2020|archive-date=15 September 2022|archive-url=https://web.archive.org/web/20220915133926/https://patents.google.com/patent/US6094003A/en|url-status=live}}</ref> or invar alloy<ref>{{Cite web|url=https://patents.google.com/patent/US4528246A/en|title=Shadow mask|access-date=5 December 2020|archive-date=15 September 2022|archive-url=https://web.archive.org/web/20220915133947/https://patents.google.com/patent/US4528246A/en|url-status=live}}</ref> that is coated with photoresist, which is baked to solidify it, exposed to UV light through photomasks, developed to remove unexposed resist, the metal is etched using liquid acid, and then the photoresist is removed. One photomask has larger dark spots than the other, this creates tapered apertures.<ref>{{Cite web | url=http://www.earlytelevision.org/pdf/manufacture_of_color_pic_tubes.pdf | title=Manufacture of Color Picture Tubes | archive-url=https://web.archive.org/web/20210126133215/https://www.earlytelevision.org/pdf/manufacture_of_color_pic_tubes.pdf | archive-date=26 January 2021 }}</ref> The shadow mask is installed to the screen using metal pieces<ref>{{Cite web|url=https://patents.google.com/patent/US6130501A/en|title=Shadow mask mounting arrangement for color CRT|access-date=5 December 2020|archive-date=3 February 2021|archive-url=https://web.archive.org/web/20210203162121/https://patents.google.com/patent/US6130501A/en|url-status=live}}</ref> or a rail or frame<ref>{{Cite web|url=https://patents.google.com/patent/US6628058B2/en|title=Flat tension mask type cathode ray tube|access-date=5 December 2020|archive-date=18 November 2020|archive-url=https://web.archive.org/web/20201118075407/https://patents.google.com/patent/US6628058B2/en|url-status=live}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/JP2005524944A/en|title=Cathode ray tube with bracket for mounting a shadow mask frame|access-date=5 December 2020|archive-date=18 August 2021|archive-url=https://web.archive.org/web/20210818015221/https://patents.google.com/patent/JP2005524944A/en|url-status=live}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US5982085A/en|title=Color cathode ray tube with improved shadow mask mounting system|access-date=5 December 2020|archive-date=1 April 2022|archive-url=https://web.archive.org/web/20220401003421/https://patents.google.com/patent/US5982085A/en|url-status=live}}</ref> that is fused to the funnel or the screen glass respectively,<ref>{{Cite web | url=https://pure.tue.nl/ws/files/1904406/200211486.pdf | title=Innovative use of magnetic quadrupoles in cathode-ray tubes | archive-url=https://web.archive.org/web/20201112200421/https://pure.tue.nl/ws/files/1904406/200211486.pdf | archive-date=12 November 2020 }}</ref> holding the shadow mask in tension to minimize warping (if the mask is flat, used in flat screen CRT computer monitors) and allowing for higher image brightness and contrast. Bimetal springs may be used in CRTs used in TVs to compensate for warping that occurs as the electron beam heats the shadow mask, causing thermal expansion.<ref>{{Cite web|url=https://books.google.com/books?id=Frbtc4mssNQC&q=crt+shadow+mask+metal&pg=PA24|title=Popular Science|first=Bonnier|last=Corporation|date=5 August 1986|publisher=Bonnier Corporation|via=Google Books|access-date=16 December 2020|archive-date=31 March 2022|archive-url=https://web.archive.org/web/20220331010316/https://books.google.com/books?id=Frbtc4mssNQC&q=crt+shadow+mask+metal&pg=PA24|url-status=live}}</ref>