Archive through March 12, 2009

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Author Message Russell John (Unregistered Guest) Unregistered guest Posted on Wednesday, March 04, 2009 - 07:46 pm:    I am working on a project where there are glass doors for showers, water closet enclosures as well as glass separating two bathroom areas. The intent was to have tempered glass installed but the language used was "safety glass" and the GC is claiming that annealed is safety glass. Is there a standard that can be referenced that provides clarification between the two or should more specific language been used? Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 744 Registered: 03-2003 Posted on Wednesday, March 04, 2009 - 10:37 pm:    Annealed is NOT safety glass. It is standard flat glass conforming to ASTM C 1036. If you put a sample of annealed glass through the testing for safety glass per CPSC 16 CFR 1201 and any first grader will come to the conclusion that annealed glass had failed the test. Just to prove the point, challenge him to see if he can find a supplier of annealed glass that will provide either the permanent designation applied to the glass or a certificate indicating that the glass is safety glass in accordance with the 2006 IBC. Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP RLGA Technical Services www.specsandcodes.com John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1017 Registered: 03-2002 Posted on Thursday, March 05, 2009 - 08:31 am:    Saftey glass must conform to Consumer Product Safety Commission requirements that Ron mentions. That regulation also prohibits any manufacturer of doors, including shower doors, from using anything but safety glass in their products. Your contractor would be unable to provide a shower door that's not tempered. CPSC 16 CFR 1201 gives other specific places where safety glass is required, but the IBC adds locations beyond those required by th CPSC. Safety glass can either be tempered or laminated, but never annealed. J. Peter Jordan Senior Member Username: jpjordan Post Number: 314 Registered: 05-2004 Posted on Saturday, March 07, 2009 - 02:10 pm:    It is confusing, but the "annealing" is an integral part of producing the float glass. Tempering (and heat strengthening) are separate processes. The glass industry uses the term "annealed glass" and "float glass" interchangeably (swapping them out almost every other sentence) without realizing how confusing it can be. Laminated glass may also meet the requirements for "safety glass", but it is usually 2-1/2 to 3 times more expensive than tempered glass. Curt Norton, CSI, CCS Senior Member Username: curtn Post Number: 137 Registered: 06-2002 Posted on Saturday, March 07, 2009 - 04:36 pm:    Just to add to the confusion, laminated safety glass can be made with annealed glass or tempered glass. Steven Hauk Senior Member Username: sh1net Post Number: 17 Registered: 12-2004 Posted on Monday, March 09, 2009 - 12:42 am:    The term "safety glass" seems to be too vague for a specification. Note in this page CPSC 16 CFR 1201 lists annealed glass as exempt from the accelerated environmental durability tests, just like it does wired glass and tempered... http://frwebgate.access.gpo.gov/cgi-bin/get-cfr.cgi?TITLE=16&PART=1201&SECTION=4&YEAR=2000&TYPE=TEXT John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1018 Registered: 03-2002 Posted on Monday, March 09, 2009 - 08:52 am:    Safety Glass is not too vague for a specification if you are willing to accept either laminated or tempered. And it would certainly exclude annealed as this contractor proposes. Accelerated durability testing checks to see if the laminating or coating will be subject to deterioration; something not applicable to monolithic tempered glass. Steven Hauk Senior Member Username: sh1net Post Number: 18 Registered: 12-2004 Posted on Monday, March 09, 2009 - 09:36 am:    Is it common to specify it that way? Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 745 Registered: 03-2003 Posted on Monday, March 09, 2009 - 11:19 am:    The IBC uses the term "Safety Glazing" in Section 2406, which specifies the requirements for safety glass and the required locations. Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP RLGA Technical Services www.specsandcodes.com John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1020 Registered: 03-2002 Posted on Monday, March 09, 2009 - 01:01 pm:    I would not say it is common to specify safety glass without specifying which type. However, there are cases where I have done it. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 861 Registered: 07-2002 Posted on Monday, March 09, 2009 - 05:43 pm:    I have often specified safety glazing as that glass that meets the code if it isn't important to the design which type -- for example, glass used at relights which are fully framed or other conditions where the edges and color aren't critical to the design. Generally the choice will be tempered glass since as noted above, laminated is more expensive. The question above (ie, that annealed glass is "safety glass", which it clearly is not) points out to me that on many projects I've had in the past few years, its possible to get contractors who really are very naive about materials and methods. I used to think that my job meant that I was teaching the younger staff in the office -- now it means that I'm teaching the Contractor's staff as well... Bill Coady CSI, CCPR Senior Member Username: billcoady Post Number: 6 Registered: 06-2006 Posted on Thursday, March 12, 2009 - 12:30 am:    Comments about the question and other comments: 1) The GC is wrong. Annealed glass is not safety glass. 2) "Float" glass is the glass made by pouring or spilling molten glass onto a bed of molten tin. The glass "floats" on top of the tin. As it does this it becomes what is called the "ribbon". This is the common way for today's typical flat glass to be manufactured. Another common type of architectural glass is pattern glass, also differentiated as "rolled pattern". The most common of this type of glass is the ubiquitous "obscure" glass called pin-head, P-516, or P-62. Rolled pattern is slowly cooled also into an annealed state. Rolled pattern is not float glass. It goes from the furnace and tank into and through a set of rollers that imprint the glass with the desired pattern. There are other types of glass manufacturing processes, such as cast, blown, etc. 3) The annealing process is where the glass is slowly cooled after the ribbon leaves the "tin bath" and enters the annealing "lehr" (named after the guy that created the process). In the lehr the ribbon of glass is cooled from about 1100F to about 200F as it travels 400-600 feet. When it has been slowly cooled like this most of the stress has been removed or relieved. At the end of the annealing lehr the glass is inspected (with electronic digital scanning equipment and sometimes manually), defects identified, and then the ribbon is cut on line into various sizes at the same time the automated equipment cuts around and rejects the defects. 4) Annealed glass can then be further fabricated by heat treating to create heat strengthened (HS)or fully tempered glass (FT). This process is where the glass is cut to size, reheated to about 1100-1500F and then quickly cooled or "quenched". The rapid cooling creates a zone of compression around the outer thickness/layer of the glass and a zone of tension in the inner layer of the glass (from one side to the other the thickness of the zones equal roughly 20% compression, 60% tension, 20% compression). The speed at which the glass is quenched determines whether the glass becomes heat strengthened or fully tempered. HS glass must measure 2500-7500 psi compression. FT must be a minimum of 10,000 psi compression. Heat strengthened glass is NOT safety glass. Fully tempered glass is considered safety glass under ANSI and CSPC guidelines and the model codes. Laminated glass with a .030" interlayer, whether the glass is annealed, heat strengthened, or tempered, is considered safety glazing. FYI- In Canada the interlayer can be as thin as .015" in some applications and is considered safety glazing. 5) Tempered glass can originate as float, rolled pattern, or cast. Annealed glass can originate as float, rolled pattern, or cast. Annealed is a state of glass. Float is one of many processes to make glass.