<p>Is there actually a way to determine whether the sheet of glass that one has received from a Chinese supplier on eBay is actually a sheet of Borosilicate glass, and not just a piece of normal glass intended for glazing purposes?</p>

<p>Are there any laminations, or markings/features, visible under a certain light or if the sheet is viewed at a particular angle?</p>

<p>I ask because most of the 200 x 300 mm sheets on eBay are priced at around £16 - £26, but there are a few priced at just £10, which still claim to be toughened glass, although they do not mention the word Borosilicate, such as this one, <a href="http://www.ebay.co.uk/itm/300x200x3mm-3D-Printer-Heated-Bed-Toughened-Glass-Clear-Build-Plate-UK-STOCK-/302067007035" rel="nofollow noreferrer">300x200x3mm 3D Printer Heated Bed Toughened Glass Clear Build Plate UK STOCK</a>. </p>

<p>To paraphrase, "Usually if things seem to good to be true, then they are probably fake." However, I wondered whether it was worth a punt as it is only £10, and then if I would be able to verify its veracity once it was in my hands.</p>

[{'answer_id': 3099, 'author': 'Sean Houlihane', 'author_id': 4927, 'author_profile': 'https://3dprinting.stackexchange.com/users/4927', 'pm_score': 3, 'selected': True, 'text': '<p>Google turned up this thread: <a href="http://arstechnica.com/civis/viewtopic.php?t=96214" rel="nofollow noreferrer">http://arstechnica.com/civis/viewtopic.php?t=96214</a></p>\n\n<p>There don\'t seem to be any easy, definitive tests. You have two main options, both of which seem to require a fairly high level of laboratory skill (but nothing fancy in terms of equipment).</p>\n\n<p>The refractive index of Borosilicate glass is very similar to vegetable oil (implying no reflection from a boundary if you have a pool of oil on the glass).</p>\n\n<p>The density of the glass can be measured too, using a water bath. This should also be able to give a fairly accurate answer.</p>\n\n<p>Stress testing seems the most reliable way to determine if you have a \'good\' sample, but may be more expensive.</p>\n'}, {'answer_id': 7157, 'author': 'Anonymous', 'author_id': 13180, 'author_profile': 'https://3dprinting.stackexchange.com/users/13180', 'pm_score': 0, 'selected': False, 'text': "<p>All you have to do is submerge your sample of glass into mineral oil. If it seems to disappear, it's borosilicate.</p>\n"}, {'answer_id': 7184, 'author': 'NightKnight on Cloudinsidr.com', 'author_id': 13220, 'author_profile': 'https://3dprinting.stackexchange.com/users/13220', 'pm_score': -1, 'selected': False, 'text': '<blockquote>\n  <p>"toughened" glass,</p>\n</blockquote>\n\n<p>Lead, cadmium and barium would have that effect. It goes without saying that you wouldn\'t want that kind of glass anywhere near your neighborhood. </p>\n\n<p>Even those items that mention borosilicate glass in the product description may have never seen any boron. </p>\n\n<p>Some studies have found that more than 90% of items sourced from China are fraudulently labeled. There is no enforcement. </p>\n\n<p>While stats say nothing about any particular sample, I\'d certainly keep them in mind. </p>\n'}]
['https://3dprinting.stackexchange.com/questions/3098', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/4762/']