Editing Cathode-ray tube (section)

===Body===
[[File:Coating CRTs at Research Enterprises.jpg|thumb|Small circular CRTs during manufacturing in 1947 (screens being coated with phosphor)]]
[[File:Mini Star 416-8834.jpg|thumb|A portable monochrome CRT TV]]
[[File:Trinitron computer-monitor.jpg|thumb|A [[Trinitron]] CRT computer monitor]]
[[File:Mini Star 416 - cathode ray tube-2140.jpg|thumb|A monochrome CRT as seen inside a TV. The CRT is the single largest component in a CRT TV.]]
[[File:Macintosh Plus interior.jpg|thumb|A monochrome CRT as seen inside a [[Macintosh Plus]] computer]]
The body of a CRT is usually made up of three parts: A screen/faceplate/panel, a cone/funnel, and a neck.<ref>{{Cite patent |country=EP |number=0088122B1 |url=https://patents.google.com/patent/EP0088122B1/en |title=Large metal cone cathode ray tubes, and envelopes therefor}} calls it faceplate {{Cite patent |country=US |number=20040032200A1 |url=https://patents.google.com/patent/US20040032200A1/en|title=CRT having a contrast enhancing exterior coating and method of manufacturing the same}} also calls it faceplate {{Cite patent |country=US |number=20060132019A1 |url=https://patents.google.com/patent/US20060132019A1/en|title=Funnel for use in a cathode ray tube}}</ref><ref>{{cite web |url=https://www.illinoisrecycles.org/wp-content/uploads/2014/10/150618_T_3.1_ChrisCahnovsky.pdf |archive-url=https://web.archive.org/web/20210228121122/https://www.illinoisrecycles.org/wp-content/uploads/2014/10/150618_T_3.1_ChrisCahnovsky.pdf |archive-date=2021-02-28 |url-status=live |title= Case study|last= Cahnovsky|first=Chris |website=www.illinoisrecycles.org |access-date=2020-12-11}}</ref><ref name="auto34">{{cite journal |last1=Ha |first1=Kuedong |last2=Shin |first2=Soon-Cheol |last3=Kim |first3=Do-Nyun |last4=Lee |first4=Kue-Hong |last5=Kim |first5=Jeong-Hoon |title=Development of a 32-in. slim CRT with 125° deflection |journal=Journal of the Society for Information Display |date=2006 |volume=14 |issue=1 |pages=65 |doi=10.1889/1.2166838 |s2cid=62697886 }}</ref><ref name="auto104">{{cite web |url=https://dnr.mo.gov/env/hwp/escrap/docs/crttcp99.pdf |title=Characterization of Lead Leachability From Cathode Ray Tubes Using the Toxicity Characteristic Leaching Procedure |date=1999 |website=dnr.mo.gov |access-date=2020-12-11 |archive-date=6 March 2021 |archive-url=https://web.archive.org/web/20210306075506/https://dnr.mo.gov/env/hwp/escrap/docs/crttcp99.pdf |url-status=dead }}</ref><ref name="auto73">{{Cite web|url=https://www.vice.com/en/article/americas-television-graveyards/|title=America's Television Graveyards|website=Vice.com|date=16 February 2017 }}</ref> The joined screen, funnel and neck are known as the bulb or envelope.<ref name="auto42"/>

The neck is made from a glass tube<ref>{{Cite patent |country=CN |number=1545118A |url=https://patents.google.com/patent/CN1545118A/en |title=Processing technique for straight tube necking glass cone for CRT}}</ref> while the funnel and screen are made by pouring and then pressing glass into a mold.<ref>{{Cite patent |country=US |number=3484225A |url=https://patents.google.com/patent/US3484225A/en|title=Method of reforming glass face plates on a shaping mold}}</ref><ref>{{Cite patent |country=US |number=7093732B1 |url=https://patents.google.com/patent/US7093732B1/en|title=CRT funnel with positioning reference portions}}</ref><ref>{{Cite patent |country=US |number=20060001351A1 |url=https://patents.google.com/patent/US20060001351A1/en|title=Glass panel and a cathode ray tube including the same}}</ref><ref>{{Cite patent |country=US |number=3264080A |url=https://patents.google.com/patent/US3264080A/en|title=Method for forming rectangular face plate}}</ref><ref>{{Cite patent |country=JP |number=3539635B2 |url=https://patents.google.com/patent/JP3539635B2/en |title=Funnel for cathode ray tube}}</ref> The glass, known as CRT glass<ref>{{Cite web|url=https://ric.werecycle.eu/c/CRT_tubes_and_glass|title=6. CRT Glass|website=ric}}</ref><ref>{{Cite web|url=https://www.epa.gov/hw/frequent-questions-about-regulation-used-cathode-ray-tubes-crts-and-crt-glass|title=Frequent Questions About the Regulation of Used Cathode Ray Tubes (CRTs) and CRT Glass|date=22 February 2016|website=US EPA}}</ref> or TV glass,<ref>{{Cite book|url=https://books.google.com/books?id=MpQR01fTv7YC&q=tv+glass&pg=PA11|title=Quality Wars: The Triumphs and Defeats of American Business|first=Jeremy|last=Main|date=11 May 2010|publisher=Simon and Schuster|isbn=9781439138458|via=Google Books}}</ref> needs special properties to shield against x-rays while providing adequate light transmission in the screen or being very electrically insulating in the funnel and neck.  The formulation that gives the glass its properties is also known as the melt. The glass is of very high quality, being almost contaminant and defect free. Most of the costs associated with glass production come from the energy used to melt the raw materials into glass. Glass furnaces for CRT glass production have several taps to allow molds to be replaced without stopping the furnace, to allow production of CRTs of several sizes. Only the glass used on the screen needs to have precise optical properties.

The optical properties of the glass used on the screen affect color reproduction and purity in color CRTs. Transmittance, or how transparent the glass is, may be adjusted to be more transparent to certain colors (wavelengths) of light. Transmittance is measured at the center of the screen with a 546&nbsp;nm wavelength light, and a 10.16mm thick screen. Transmittance goes down with increasing thickness. Standard transmittances for Color CRT screens are 86%, 73%, 57%, 46%, 42% and 30%. Lower transmittances are used to improve image contrast but they put more stress on the electron gun, requiring more power on the electron gun for a higher electron beam power to light the phosphors more brightly to compensate for the reduced transmittance.<ref name="auto94"/><ref name="auto4">{{cite web |url=http://gradllc.com/images/Def.pdf |archive-url=https://web.archive.org/web/20040909183710/http://gradllc.com/images/Def.pdf |archive-date=2004-09-09 |url-status=live |title= Deflection|website=gradllc.com |access-date=2020-12-11}}</ref> The transmittance must be uniform across the screen to ensure color purity. The radius (curvature) of screens has increased (grown less curved) over time, from 30 to 68 inches, ultimately evolving into completely flat screens, reducing reflections. The thickness of both curved<ref name="auto22">{{Cite web|url=http://www.lgphilips-displays.com:80/download/Catalogue-CDT.pdf|title=Catalogue-CDT|archive-url=https://web.archive.org/web/20030317014046/http://www.lgphilips-displays.com:80/download/Catalogue-CDT.pdf |archive-date=17 March 2003 }}</ref> and flat screens gradually increases from the center outwards, and with it, transmittance is gradually reduced. This means that flat-screen CRTs may not be completely flat on the inside.<ref name="auto22"/><ref>{{Cite patent |country=US |number=6806636B2 |url=https://patents.google.com/patent/US6806636B2/en|title=Flat CRT with improved coating}}</ref>

The glass used in CRTs arrives from the glass factory to the CRT factory as either separate screens and funnels with fused necks, for Color CRTs, or as bulbs made up of a fused screen, funnel and neck. There were several glass formulations for different types of CRTs, that were classified using codes specific to each glass manufacturer. The compositions of the melts were also specific to each manufacturer.<ref name="glassts">{{cite web |url=https://www.glass-ts.com/userfiles/files/2003-08%20New%20Approach%20to%20Cathode%20Ray%20Tube%20(CRT)%20Recycling.pdf |title=GW-12.10-130: NEW APPROACH TO CATHODE RAY TUBE (CRT) RECYCLING |date=2003 |website=www.glass-ts.com |access-date=2020-12-11 |archive-date=13 November 2020 |archive-url=https://web.archive.org/web/20201113001416/https://www.glass-ts.com/userfiles/files/2003-08%20New%20Approach%20to%20Cathode%20Ray%20Tube%20(CRT)%20Recycling.pdf |url-status=dead }}</ref> Those optimized for high color purity and contrast were doped with Neodymium, while those for monochrome CRTs were tinted to differing levels, depending on the formulation used and had transmittances of 42% or 30%.<ref name="auto38">{{cite web |url= https://spie.org/samples/TT54.pdf |archive-url=https://web.archive.org/web/20120907080716/http://spie.org/samples/TT54.pdf |archive-date=2012-09-07 |url-status=live|title= CRT Glass|website=spie.org |access-date=2020-12-11}}</ref> Purity is ensuring that the correct colors are activated (for example, ensuring that red is displayed uniformly across the screen) while convergence ensures that images are not distorted. Convergence may be modified using a cross hatch pattern.<ref name="auto85">{{Cite web|url=https://www.repairfaq.org/samnew/tvfaq/tvccrtssa.htm|title=SER FAQ: TVFAQ: Color CRTs - shadow masks and aperture grills|website=www.repairfaq.org}}</ref><ref name="auto48">{{Cite web|url=https://www.repairfaq.org/samnew/tvfaq/tvcrtcona.htm|title=SER FAQ: TVFAQ: CRT convergence adjustment|website=www.repairfaq.org}}</ref><ref>{{Cite web|url=https://www.mediacollege.com/video/test-patterns/convergence/|title=Convergence Test Patterns|website=www.mediacollege.com}}</ref>

CRT glass used to be made by dedicated companies<ref>{{Cite web|url=https://www.eetimes.com/corning-asahi-video-to-sell-plant-assets-to-chinese-supplier/|title=Corning Asahi Video to sell plant assets to Chinese supplier &#124; EE Times|date=10 June 2003 }}</ref> such as [[AGC Inc.]],<ref>{{Cite web|url=http://www.digitimes.com/news/a20060725A6027.html|title=CPT expects limited impact from Asahi Glass CRT plant closure in Taiwan|website=DIGITIMES|date=25 July 2006 }}</ref><ref>{{Cite web|url=https://www.glassonline.com/asahi-techno-vision-to-close-singapore-plant/|title=Asahi Techno Vision to close Singapore plant|date=12 June 2007}}</ref><ref>{{Cite web|url=https://www.glassonline.com/asahi-glass-restructures-crt-funnel-manufacturing/|title=Asahi Glass restructures CRT funnel manufacturing|date=13 January 2005}}</ref> [[O-I Glass]],<ref>{{Cite web|url=https://www.neg.co.jp/en/company/history/|title=History|website=Nippon Electric Glass Co., Ltd.}}</ref> Samsung Corning Precision Materials,<ref>{{Cite web|url=https://www.koreatimes.co.kr/www/tech/2020/12/693_100541.html|title=4 CRT glass makers fined for price fixing|date=11 December 2011|website=koreatimes}}</ref> [[Corning Inc.]],<ref>{{Cite web|url=https://www.photonics.com/Articles/Corning_to_Close_Plant_and_Cut_1000_Jobs/a15760|title=Corning to Close Plant and Cut 1000 Jobs|website=www.photonics.com}}</ref><ref>{{Cite web|url=https://www.zdnet.com/article/corning-to-close-tv-glass-plant/|title=Corning to close TV glass plant|first=Richard|last=Shim|website=ZDNet}}</ref> and [[Nippon Electric Glass]];<ref>{{Cite web|url=https://www.bcnretail.com/news/detail/050901_2045.html|title=日本電気硝子、CRT用ガラスの国内生産を9月末で停止、国内需要の消滅に対応|website=BCN＋R}}</ref> others such as Videocon, Sony for the US market and Thomson made their own glass.<ref name="auto72">{{Cite web|url=https://resource-recycling.com/e-scrap/2016/03/03/videocon-begins-accepting-crt-glass-again/|title=Videocon begins accepting CRT glass again|first=Bobby|last=Elliott|date=3 March 2016}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=BAmBhJta85wC&q=thomson+picture+tube&pg=PA4|title=Industry and Trade Summary: Television Picture Tubes and other Cathode-Ray Tubes|publisher=DIANE Publishing|isbn=9781457825903|via=Google Books}}</ref><ref>{{Cite web|url=http://archive.glassonline.com/site/news/topic/Sector-trends/id/4797/American-Video-Glass-Company-TV-glass-plant-officially-dedicated|title=American Video Glass Company: TV glass plant officially dedicated|website=archive.glassonline.com|access-date=8 December 2020|archive-date=21 October 2021|archive-url=https://web.archive.org/web/20211021165012/http://archive.glassonline.com/site/news/topic/Sector-trends/id/4797/American-Video-Glass-Company-TV-glass-plant-officially-dedicated|url-status=dead}}</ref><ref>{{cite web |url=https://www.bizjournals.com/pittsburgh/stories/2006/12/04/daily32.html |title= Daily stories|website=2006 www.bizjournals.com|access-date=2020-12-11}}</ref><ref name="auto95">{{Cite web|url=http://www.gic.jp/museum/tv_tale/tv_tale02.html|title=テレビ今昔物語|website=www.gic.jp}}</ref>

The funnel and the neck are made of leaded potash-soda glass or lead silicate glass<ref name="auto50"/> formulation to shield against x-rays generated by high voltage electrons as they decelerate after striking a target, such as the phosphor screen or [[shadow mask]] of a color CRT. The velocity of the electrons depends on the anode voltage of the CRT; the higher the voltage, the higher the speed.<ref name="auto2">{{Cite web|url=https://www2.physics.ox.ac.uk/accelerate/resources/demonstrations/cathode-ray-tube|title=Cathode ray tube &#124; University of Oxford Department of Physics|website=www2.physics.ox.ac.uk}}</ref> The amount of x-rays emitted by a CRT can also lowered by reducing the brightness of the image.<ref>{{Cite web|url=http://repairfaq.cis.upenn.edu/Misc/samnew/tvfaq/tvsibwaxray.htm|title=SER FAQ: TVFAQ: Should I be worried about X-ray exposure while servicing a TV or monitor?|website=repairfaq.cis.upenn.edu|access-date=8 December 2020|archive-date=1 November 2020|archive-url=https://web.archive.org/web/20201101031818/http://repairfaq.cis.upenn.edu/Misc/samnew/tvfaq/tvsibwaxray.htm|url-status=dead}}</ref><ref>{{Cite web|url=http://repairfaq.cis.upenn.edu/Misc/samnew/tvfaq/tvxrayoem.htm|title=SER FAQ: TVFAQ: X-ray and other EM emission from my TV or monitor?|website=repairfaq.cis.upenn.edu|access-date=8 December 2020|archive-date=1 November 2020|archive-url=https://web.archive.org/web/20201101131639/http://repairfaq.cis.upenn.edu/Misc/samnew/tvfaq/tvxrayoem.htm|url-status=dead}}</ref><ref name="auto35">{{Cite magazine|title=X-Rays from TV Sets - Are They Harmful? <!--https://www.rfcafe.com/references/radio-news/tv-set-x-rays-radio-tv-news-november-1958.htm-->|date=November 1958|magazine=Radio News}}</ref><ref name="auto104"/> Leaded glass is used because it is inexpensive,<ref name="auto1">{{Cite web|url=https://patents.google.com/patent/JP2000128571A/en?q=(cathode+ray+tube+lead+glass+economical)&oq=cathode+ray+tube+lead+glass+economical&page=1|title=陰極線管用のガラス組成物および陰極線管}}</ref> while also shielding heavily against x-rays, although some funnels may also contain barium.<ref name="Lee & Hsi 2002">{{cite journal |last1=Lee |first1=Ching-Hwa |last2=Hsi |first2=Chi-Shiung |title=Recycling of Scrap Cathode Ray Tubes |journal=Environmental Science & Technology |date=1 January 2002 |volume=36 |issue=1 |pages=69–75 |doi=10.1021/es010517q |pmid=11811492 |bibcode=2002EnST...36...69L }}</ref><ref>{{Cite book|url=https://books.google.com/books?id=z4Ha0AYdon4C&q=cathode+ray+tube+funnel+lead+glass+inexpensive&pg=PA57|title=Lead-free Electronics|first1=Sanka|last1=Ganesan|first2=Michael G.|last2=Pecht|date=31 March 2006|publisher=John Wiley & Sons|isbn=9780470007792|via=Google Books}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=FvkqeL4IDMwC&q=cathode+ray+tube+funnel+lead+glass+inexpensive&pg=PA5|title=Image Performance in CRT Displays|first=Kenneth|last=Compton|date=5 December 2003|publisher=SPIE Press|isbn=9780819441447|via=Google Books}}</ref><ref name="auto38"/> The screen is usually instead made out of a special lead-free silicate<ref name="auto50"/> glass formulation with barium and strontium to shield against x-rays, as it doesn't brown unlike glass containing lead.<ref name="auto1"/><ref>{{Cite book|url=https://books.google.com/books?id=nGsoDwAAQBAJ&dq=crt+glass+browning&pg=RA1-PA5|title=Introduction to Glass Science and Technology|first=James E.|last=Shelby|date=6 November 2015|publisher=Royal Society of Chemistry|isbn=978-1-78262-511-7 |via=Google Books}}</ref> Another glass formulation uses 2–3% of [[lead]] on the screen.<ref name="auto104"/> Alternatively zirconium can also be used on the screen in combination with barium, instead of lead.<ref>{{cite book | url=https://books.google.com/books?id=T1NS5wI3H4UC&dq=projection+crt+radiation+browning&pg=PA227 | isbn=978-0-306-44191-2 | title=Color in Electronic Displays | date=30 April 1992 | publisher=Springer }}</ref>
[[File:Old TV3.jpg|thumb|Soviet TV set from 1960s photographed from backside]]

Monochrome CRTs may have a tinted barium-lead glass formulation in both the screen and funnel, with a potash-soda lead glass in the neck; the potash-soda and barium-lead formulations have different thermal expansion coefficients. The glass used in the neck must be an excellent electrical insulator to contain the voltages used in the electron optics of the electron gun, such as focusing lenses. The lead in the glass causes it to brown (darken) with use due to x-rays, usually the CRT cathode wears out due to cathode poisoning before browning becomes apparent. The glass formulation determines the highest possible anode voltage and hence the maximum possible CRT screen size. For color, maximum voltages are often 24–32&nbsp;kV, while for [[monochrome]] it is usually 21 or 24.5&nbsp;kV,<ref name="auto63">{{Cite book|url=https://books.google.com/books?id=FvkqeL4IDMwC&q=crt+venting&pg=PA9|title=Image Performance in CRT Displays|first=Kenneth|last=Compton|date=5 December 2003|publisher=SPIE Press|isbn=9780819441447|via=Google Books}}</ref> limiting the size of monochrome CRTs to 21&nbsp;inches, or ~1&nbsp;kV per inch. The voltage needed depends on the size and type of CRT.<ref name="auto3">{{Cite patent |country=US |number=5096445A |url=https://patents.google.com/patent/US5096445A/en|title=Anode connector assembly for a cathode ray tube}}</ref> Since the formulations are different, they must be compatible with one another, having similar thermal expansion coefficients.<ref name="auto38"/> The screen may also have an anti-glare or anti-reflective coating,<ref>{{Cite patent |country=US |number=5404073A |url=https://patents.google.com/patent/US5404073A/no|title=Antiglare/antistatic coating for CRT}}</ref><ref name="auto4"/><ref>{{Cite web|url=https://www.tomshardware.com/reviews/comparison,440.html|title=Comparison: Twelve 19" CRT Monitors|first=Philippe|last=Ramelet|date=March 19, 2002|website=Tom's Hardware}}</ref> or be ground to prevent reflections.<ref>{{Cite patent |country=US |number=4884006A |url=https://patents.google.com/patent/US4884006A/en |title=Inner surface specular reflection suppression in flat CRT faceplate}}</ref> CRTs may also have an anti-static coating.<ref name="auto4"/><ref>{{Cite patent |country=US |number=6590352B1 |url=https://patents.google.com/patent/US6590352B1/en|title=Electrical grounding of CRT antistatic/antireflective coating}}</ref><ref name="auto94"/>

The leaded glass in the funnels of CRTs may contain 21–25% of [[lead oxide]] (PbO),<ref name="auto81">{{Cite patent |country=US |number=6163106A |url=https://patents.google.com/patent/US6163106A/en|title=Color cathode ray tube and water resistant glass frit}}</ref><ref>{{cite web |url=https://ipen.org/sites/default/files/documents/Looking-through-glass-CRT-recycling-in-India.pdf |archive-url=https://web.archive.org/web/20201001051655/https://ipen.org/sites/default/files/documents/Looking-through-glass-CRT-recycling-in-India.pdf |archive-date=2020-10-01 |url-status=live |title= Looking through the glass|website=ipen.org |access-date=2020-12-11}}</ref><ref name="glassts"/> The neck may contain 30–40% of lead oxide,<ref>{{Cite web |url=https://www.glass-ts.com/userfiles/files/2003-08%2520New%2520Approach%2520to%2520Cathode%2520Ray%2520Tube%2520(CRT)%2520Recycling.pdf |title=Archived copy |access-date=20 February 2021 |archive-date=7 March 2021 |archive-url=https://web.archive.org/web/20210307115851/https://www.glass-ts.com/userfiles/files/2003-08%20New%20Approach%20to%20Cathode%20Ray%20Tube%20(CRT)%20Recycling.pdf |url-status=dead }}</ref><ref>{{cite journal |last1=Xu |first1=Qingbo |last2=Li |first2=Guangming |last3=He |first3=Wenzhi |last4=Huang |first4=Juwen |last5=Shi |first5=Xiang |title=Cathode ray tube (CRT) recycling: Current capabilities in China and research progress |journal=Waste Management |date=August 2012 |volume=32 |issue=8 |pages=1566–1574 |doi=10.1016/j.wasman.2012.03.009 |pmid=22542858 |bibcode=2012WaMan..32.1566X }}</ref> and the screen may contain 12% of [[barium oxide]], and 12% of [[strontium oxide]].<ref name="auto50"/> A typical CRT contains several kilograms of lead as lead oxide in the glass<ref name="auto73"/> depending on its size; 12 inch CRTs contain 0.5&nbsp;kg of lead in total while 32&nbsp;inch CRTs contain up to 3&nbsp;kg.<ref name="auto50"/> Strontium oxide began being used in CRTs, its major application, in the 1970s.<ref>{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/strontium/myb1-2007-stron.pdf|title = Mineral Yearbook 2007:Strontium|first1 = Joyce A.|last1 = Ober|first2 = Désirée E.|last2 = Polyak|publisher = United States Geological Survey|access-date = 2009-09-14}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=G6c7AQAAMAAJ&q=faceplate+glass+production+%2C+strontium%27s+major+end+use+since+the+early+1970s&pg=RA6-SA74-PA1|title=Minerals Yearbook|date=8 May 2011|publisher=Bureau of Mines|isbn=9781411332270|via=Google Books}}</ref> Before this, CRTs used lead on the faceplate.<ref name="auto74"/>

Some early CRTs used a metal funnel insulated with polyethylene instead of glass with conductive material.<ref name="auto59"/> Others had ceramic or blown Pyrex instead of pressed glass funnels.<ref>{{Cite web|url=https://www.earlytelevision.org/racs_pyrex_rebuild.html|title=RACS - Pyrex CRT Rebuilding|website=www.earlytelevision.org}}</ref><ref>{{cite web |url=http://www.nostalgiatech.co.uk/GB470885A.pdf |archive-url=https://web.archive.org/web/20191221202059/http://www.nostalgiatech.co.uk/GB470885A.pdf |archive-date=2019-12-21 |url-status=live |title= Patent specs|website= www.nostalgiatech.co.uk|access-date=2020-12-11}}</ref><ref name="auto30"/><ref>{{cite web |url=https://vintagetek.org/ceramic-strips/ |title=Ceramic strips |website=vintagetek.org |format=PDF|access-date=2020-12-11}}</ref><ref name="auto69">{{Cite web|url=https://www.crtsite.com/oscilloscope-crt.html|title=The Cathode Ray Tube site. oscilloscope crt's|website=www.crtsite.com}}</ref> Early CRTs did not have a dedicated anode cap connection; the funnel was the anode connection, so it was live during operation.<ref name="auto53">{{Cite web|url=https://www.oldtellys.co.uk/otmonotube.html|title=The Monochrome Tube|website=www.oldtellys.co.uk}}</ref>

The funnel is coated on the inside and outside with a conductive coating,<ref name="auto60">{{Cite web|url=http://repairfaq.cis.upenn.edu/samnew/tvfaq/tvaiodc.htm|title=SER FAQ: TVFAQ: Additional information on discharging CRTs|website=repairfaq.cis.upenn.edu|access-date=8 December 2020|archive-date=1 November 2020|archive-url=https://web.archive.org/web/20201101104218/http://repairfaq.cis.upenn.edu/samnew/tvfaq/tvaiodc.htm|url-status=dead}}</ref><ref name="auto7">{{cite web |title=Manual |url=https://wiki.arcadeotaku.com/images/c/c6/Toei_TC-L292K_Manual.pdf |url-status=live |archive-url=https://web.archive.org/web/20201110232957/https://wiki.arcadeotaku.com/images/c/c6/Toei_TC-L292K_Manual.pdf |archive-date=2020-11-10 |access-date=2020-12-11 |website=wiki.arcadeotaku.com |language=JA}}</ref> making the funnel a capacitor, helping stabilize and filter the anode voltage of the CRT, and significantly reducing the amount of time needed to turn on a CRT. The stability provided by the coating solved problems inherent to early power supply designs, as they used vacuum tubes. Because the funnel is used as a capacitor, the glass used in the funnel must be an excellent electrical insulator ([[dielectric]]). The inner coating has a positive voltage (the anode voltage that can be several kV) while the outer coating is connected to ground. CRTs powered by more modern power supplies do not need to be connected to [[Ground (electricity)|ground]], due to the more robust design of modern power supplies. The value of the capacitor formed by the funnel is 5–10&nbsp;[[Nanofarad|nF]], although at the voltage the anode is normally supplied with. The capacitor formed by the funnel can also suffer from [[dielectric absorption]], similarly to other types of capacitors.<ref>{{Cite web|url=http://www.repairfaq.org/sam/crtfaq.htm|title=TV and Monitor CRT (Picture Tube) Information|website=www.repairfaq.org}}
{{Cite patent |country=US |number=3614519A |url=https://patents.google.com/patent/US3614519A/en |title=Cathode-ray tube magnetic shield}}
{{Cite patent |country=US |number=3802757A |url=https://patents.google.com/patent/US3802757A/en |title=Method of fabricating a cathode ray tube having a conductive metallic coating therein}}</ref><ref name="auto63"/><ref name="auto67">{{Cite web|url=http://www.r-type.org/exhib/aar0020.htm|title=40CB4 @ The Valve Museum|website=www.r-type.org}}</ref><ref name="auto29">{{Cite patent |country=US |number=5104686A |url=https://patents.google.com/patent/US5104686A/en |title=CRT funnel coating apparatus and method}}</ref><ref name="auto60"/><ref name="auto38"/> Because of this CRTs have to be discharged<ref name="auto15">{{cite web |url=http://www.crtsolutions.com/CRTSafety.pdf |archive-url=https://web.archive.org/web/20120617143458/http://www.crtsolutions.com/CRTSafety.pdf |archive-date=2012-06-17 |url-status=live |title= CRT Safety |website=www.crtsolutions.com |access-date=2020-12-11}}</ref> before handling to prevent injury.

The depth of a CRT is related to its screen size.<ref name="auto79">{{cite web |url=https://eti.pg.edu.pl/documents/176568/264302/module%202%20cathode%20ray%20tube.doc |title= Data|website= eti.pg.edu.pl|access-date=2020-12-11}}</ref> Usual deflection angles were 90° for computer monitor CRTs and small CRTs and 110° which was the standard in larger TV CRTs, with 120 or 125° being used in slim CRTs made since 2001–2005 in an attempt to compete with LCD TVs.<ref>Practical Television, November 2001 issue <!--https://worldradiohistory.com/hd2/IDX-UK/Technology/Technology-All-Eras/Archive-Practical-Television-IDX/00s/Television-2001-11-OCR-Page-0006.pdf--> 120° deflection
{{Cite patent |country=CN |number=101253599A |url=https://patents.google.com/patent/CN101253599A/en |title=High deflection angle CRT display }}
{{Cite web|url=http://repairfaq.cis.upenn.edu/sam/crtfaq.htm|title=TV and Monitor CRT (Picture Tube) Information|website=repairfaq.cis.upenn.edu|access-date=8 December 2020|archive-date=22 November 2020|archive-url=https://web.archive.org/web/20201122100132/http://repairfaq.cis.upenn.edu/sam/crtfaq.htm|url-status=dead}} 90 degrees in monitors, 110 in TVs</ref><ref name="auto4"/><ref name="auto9"/><ref name="auto34"/><ref name="auto45">{{Cite web|url=http://www.r-type.org/exhib/aac0001.htm|title=M14-170W @ The Valve Museum|website=www.r-type.org}}</ref> Over time, deflection angles increased as they became practical, from 50° in 1938 to 110° in 1959,<ref name="auto68"/> and 125° in the 2000s. 140° deflection CRTs were researched but never commercialized, as convergence{{Clarification needed|reason=What does "convergence" mean here?|date=December 2023}} problems were never resolved.<ref>{{Cite web|url=https://www.earlytelevision.org/color_crts.html|title=Color Picture Tubes|website=www.earlytelevision.org}}</ref>
<gallery mode="packed" heights="180px">
File:Cinescopio per televisore a schermo rettangolare, 17 pollici, deflessione 110°, bianco e nero - Museo scienza tecnologia Milano 10081 dia.jpg|A monochrome CRT with 110° deflection
File:Cinescopio per televisore a schermo rettangolare, 13 pollici, deflessione 90°, bianco e nero - Museo scienza tecnologia Milano 10082 dia.jpg|A monochrome CRT with 90° deflection
</gallery>