Editing Portland Vase (section)

==Manufacture==
[[Cameo glass]] vessels were probably all made within about two generations,{{sfn|Williams|2009|pp=292–293}} as experiments when the blowing technique (discovered in about 50 BC) was still in its infancy. Recent research suggests that the Portland Vase, like most cameo glass vessels, was made by the dip-overlay method, whereby an elongated bubble of glass was partially dipped into a [[crucible]] of white glass before the two were blown together. After cooling the white layer was cut away to form the design.{{sfn|Williams|2009|pp=293}}

Making a 19th-century copy required painstaking work. This experience suggests that creation of the original Portland Vase required two years of work. Cutting was probably performed by a skilled gem-cutter,<ref name="lierke">{{cite web|url=http://www.rosemarie-lierke.de/English/Cameo_glass/cameo_glass.html |title=Cameo glass |publisher=Rosemarie-lierke.de |access-date=16 December 2011}}</ref> possibly [[Dioskourides (artist)|Dioskourides]]. [[Engraved gem]]s are extant which are of a similar period and are signed and thought to be cut by him (Vollenweider 1966, see Gem in the collection of the [[duke of Devonshire]] "Diomedes stealing the Palladium"). This is supported by the [[Corning Museum of Glass|Corning Museum]] in their 190-page study of the vase.<ref>{{Cite journal|date=1990|title=The Portland Vase|journal=Journal of Glass Studies|volume=32}}</ref>

According to a controversial theory by [[Rosemarie Lierke]], the vase, along with the rest of Roman cameo glass, was moulded rather than cold-cut, probably using white glass powder for the white layer.<ref name="lierke"/>

Jerome Eisenberg has argued in ''Minerva'' that the vase was produced in the 16th century AD and not in antiquity, because the iconography is incoherent,<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/entertainment/arts/3169929.stm |title=Entertainment &#124; Age puzzle over 'Roman' treasure |work=BBC News |date=21 August 2003 |access-date=16 December 2011}}</ref> but this theory has not been widely accepted.<ref>{{Cite web |date=2016 |title=SARAH DANAYS' ARMS of THE PORTLAND VASE |url=https://www.harleygallery.co.uk/wp-content/uploads/2016/06/Sarah-Danays-Arms-Of-The-Portland-Vase.pdf |access-date=22 August 2022 |website=Harley Gallery |pages=3 |archive-date=22 August 2022 |archive-url=https://web.archive.org/web/20220822131414/https://www.harleygallery.co.uk/wp-content/uploads/2016/06/Sarah-Danays-Arms-Of-The-Portland-Vase.pdf |url-status=dead }}</ref>