Editing Ruby (section)

==Treatments and enhancements==
Improving the quality of gemstones by treating them is common practice. Some treatments are used in almost all cases and are therefore considered acceptable. During the late 1990s, a large supply of low-cost materials caused a sudden surge in supply of heat-treated rubies, leading to a downward pressure on ruby prices.

Improvements used include color alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them.

The most common treatment is the application of heat. Most rubies at the lower end of the market are heat treated to improve color, remove ''purple tinge'', blue patches, and silk. These heat treatments typically occur around temperatures of 1800&nbsp;°C (3300&nbsp;°F).<ref name="ThemelisRubyHeat">{{cite book|isbn=0940965100|title=The Heat Treatment of Ruby and Sapphire|publisher=Gemlab Inc.|place=Bangkok, Thailand|year=1992}}</ref> Some rubies undergo a process of low tube heat, when the stone is heated over charcoal of a temperature of about 1300&nbsp;°C (2400&nbsp;°F) for 20 to 30 minutes. The silk is partially broken, and the color is improved.

Another treatment, which has become more frequent in recent years, is <!-- to avoid false positives for 'is led/lead' typo-->[[lead glass]] filling. Filling the fractures inside the ruby with lead glass (or a similar material) dramatically improves the transparency of the stone, making previously unsuitable rubies fit for applications in jewelry.<ref>Vincent Pardieu [http://www.fieldgemology.org/Ruby_lead_glass_treatment.pdf Lead Glass Filled/Repaired Rubies] {{webarchive|url=https://web.archive.org/web/20110831062843/http://www.fieldgemology.org/Ruby_lead_glass_treatment.pdf |date=31 August 2011 }}. Asian Institute of Gemological Sciences Gem Testing Laboratory. February 2005</ref> The process is done in four steps:

# The rough stones are pre-polished to eradicate all surface impurities that may affect the process
# The rough is cleaned with [[hydrogen fluoride]]
# The first heating process during which no fillers are added. The heating process eradicates impurities inside the fractures. Although this can be done at temperatures up to 1400&nbsp;°C (2500&nbsp;°F) it most likely occurs at a temperature of around 900&nbsp;°C (1600&nbsp;°F) since the rutile silk is still intact.
# The second heating process in an electrical oven with different chemical additives. Different solutions and mixes have shown to be successful; however, mostly lead-containing glass-powder is used at present. The ruby is dipped into oils, then covered with powder, embedded on a tile and placed in the oven where it is heated at around 900&nbsp;°C (1600&nbsp;°F) for one hour in an oxidizing atmosphere. The orange colored powder transforms upon heating into a transparent to yellow-colored paste, which fills all fractures. After cooling the color of the paste is fully transparent and dramatically improves the overall transparency of the ruby.<ref>Richard W. Hughes (1997), ''Ruby & Sapphire'', Boulder, CO, RWH Publishing, {{ISBN|978-0-9645097-6-4}}</ref>

If a color needs to be added, the glass powder can be "enhanced" with copper or other metal oxides as well as elements such as sodium, calcium, potassium etc.

The second heating process can be repeated three to four times, even applying different mixtures.<ref>{{cite journal| last = Milisenda| first=C C| title=Rubine mit bleihaltigen Glasern gefullt| journal=Zeitschrift der Deutschen Gemmologischen Gesellschaft| volume=54 |issue=1| pages=35–41|publisher=Deutschen Gemmologischen Gesellschaft|year=2005|language=de}}</ref> When jewelry containing rubies is heated (for repairs) it should not be coated with boracic acid or any other substance, as this can etch the surface; it does not have to be "protected" like a diamond.

The treatment can be identified by noting bubbles in cavities and fractures using a 10× loupe.<ref>{{cite news |work= GIA Global Dispatch |publisher= Gemological Institute of America |date=16 February 2012 |url= http://www.gia.edu/research-resources/news-from-research/gia-global-dispatch/index.html |title= Lead Glass-Filled Rubies |url-status=dead |archive-url=https://web.archive.org/web/20120614070635/http://www.gia.edu/research-resources/news-from-research/gia-global-dispatch/index.html |archive-date= 14 June 2012 |access-date=22 January 2020|df= mdy-all }}</ref>