X-CEL OPTICAL COMPANY provides filtering glass lenses for a variety of occupational applications ranging from glass workers, foundry and boiler workers, jewelers, kiln and furnace workers to laser and X-Ray technicians. Another commonly used expression for filtration is "absorption" (of unwanted light rays).
Special laminated lens combinations of glass materials are also available.
Lenses for almost any need can be achieved by combining different materials in a lamination.
Call or e-mail us for availability.
The list that follows identifies filter glass lenses available from X-CEL to optical laboratories for use in Rx and plano safety eyewear. These lenses are available from many ophthalmic retailers throughout the United States. All of these glass materials were developed by Schott Glass Technologies.
Filter Glass Available From X-CEL OPTICAL
For both prescription & non-prescription use
Rose Didymium (*Rose Didymium no longer available.) Developed for high temperature glass work, this glass offers protection at the sodium line (589nm) and UV spectral wavelengths. The visible light transmittance of this glass at 3.2mm thickness is 50%, allowing good visibility indoors. This glass is dichroic, meaning it's color will look aqua green under fluorescent lighting but under natural and incandescent lights it will have a light rose color.
X-CEL offers this 1.523 index glass in the following lens styles; finished 71mm 3.2mm planos, semi-finished single vision, fused flat top 25's, 7X25 trifocals and round 22mm segments. The multifocal segments are not made of the filter glass. However, they are kept to a minimum thickness (< 1.5mm), so there remains filtration in the "near-reading" area. For full protection in the segment area the minimum thickness should be 3.2 plus the segment thickness (example; A flat top25, 6 base lens with a reading add of 2.00 should have a finished center thickness of 4.2mm thick). These are not laminated lenses! ¹They are fused multi-focals that will be chemically tempered and drop ball tested in accordance with ANZI, Z87 regulations. They are safe, durable and in most cases thinner and laminated lenses. They can be made in prescription powers. For those who are lucky enough not to need corrective vision, they can also be made in Plano (Zero) power lenses. The lenses may be mounted in a variety of safety frames, which can be found at local optical retail stores.
Rose Didymium glass should be chemically tempered in the standard crown bath or heat tempered like standard crown glass.
A.C.E. (Amethyst Contrast Enhancement) Originally developed to improve discrimination between different colored objects on flight instrument panels, this unique lens also offers excellent filtering at the sodium line (589nm) as well as moderate UV protection. Preferred by many in glass working industry this lens is darker than the rose didymium lens having 38% visible light transmittance and the amethyst color. Being dichroic, under fluorescent lighting, this lens will have a blue appearance.
X-CEL offers 1.563 refractive index ACE glass lenses in finished 71mm, 2.0mm planos, 3.2mm planos, semi-finished single vision, and laminated multi-focals.
A.C.E. glass must be chemically tempered in the standard crown bath at 530° C for 16 hours. It can not be heat tempered.
Schott SF-6 1.80 index leaded glass for X-Ray and radiation protection. This lens provides protection from scattered radiation in areas such as electro physiology, orthopedic surgery, radiology, catheterization lab, urologic procedures, and veterinarians.
X-CEL offers this glass lens in 66mm semi-finished single vision, laminated single vision and multi-focals.
This leaded glass is a softer glass and is prone to scratching unlike other glass lenses.
Schott SF-6 1.80 index leaded glass for X-Ray glass can not be chemically tempered, or air hardened in traditional ophthalmic equipment. It can be heat tempered at a lower temperature however, most ophthalmic heat tempering units do not have adjustable temperature capabilities.
Blue Light is that portion of the light spectrum from 380nm to 500nm. By filtering the blue light glare and gaze are reduced and contrast is enhanced.
²Chemical Tempering (Chemtempering) Strengthens glass lenses by putting the surface of the glass into compression. The process by which this occurs is the exchange of ions. During the chemtempering process lenses are submersed in a bath of molten slat at a prescribed temperature. The head causes the smaller ions to leave the surface of the glass and the larger ions present in the molten sat to enter it. Once the lenses are removed from the bath and cooled, they shrink. The larger ions that are now present in the surface of the lens are crowded together. This creates a compressed surface which results in a stronger lens that is more resistant to breaking.
²Chemtempering creates a uniform layer of stress. This is because the ion exchange occurs uniformly on all surfaces. Unlike the air tempering process, chemtempering has no relationship to lens thickness. This difference is evident when lenses tempered in these two ways are viewed in crossed polarized light. The air tempered lenses typically display various stress patterns; one of the most common resembles a maltese cross. In the uniformly tempered lenses, such patterns do not exist. Drop-ball tests support the superior impact strength of chemtempering.
Didymium is a mineral that when added into glass provides filtration (or absorption) at 589nm (sodium flare).
Green Crown is a "fixed tint" lens material intended for dress eyewear. These lighter shades are not intended for occupational filtering. They have good absorption in both UV & IR spectral ranges. Darker shades are often used as popular sunglass materials. Lighter shades are sometimes used as fashion tints.
Green Crown glass can, when left at a minimum center thickness of 3.4mm, have the same transmittance of some of the industrial shades of industrial green lenses;
Green Crown A @ 3.4mm center thickness is equal to the 1.7 industrial green shade.
Green Crown B @ 3.4mm center thickness is equal to the 2.0 industrial green shade.
Green Crown C @ 3.4mm center thickness is equal to the 2.5 industrial green shade.
Please note: According to the ANZI-Z80 regulations that with the exception of torch soldering, protective welding goggles, helmets or face shields must be worn for all welding applications. Even where custom made Rx eyewear can be fabricated, goggles, helmets, or face shields should be worn over the eyewear.
IR (Infrared) is the portion of the light spectrum beyond 760nm to 1m, near infrared is 760nm to 4600nm. IR filters are also known as heat filters or absorption glass.
Lamination is the process of bonding 2 or more lenses together using special adhesives specifically designed for glass lenses. The adhesives X-CEL uses were originally designed for the military and have proved to be very durable and safe. Glass laminated lenses can not be tempered chemically or head treated but they still need to be impact tested in accordance with ¹Z-87 regulations when used for safety eyewear and they must meet minimum thickness requirements. When laminated lenses are used for dress eyewear they still must be impact tested in accordance with the ANZI Z-80 standards. Theses lenses are not exempt from testing unless they are a custom made lens made to order for each individual customer.
Sodium Flare is seen as the bright yellow flame resulting from the reaction of an oxygen-rich flame and the surface of glass containing sodium. Protection from this flare that is the main purpose of didymium glasses. The exact wave length of the sodium flare is 389.3nm.
UV (Ultra Violet) is generally considered to the the portion of the light spectrum from 290nm to 380nm. It is invisible to the human eye and can be damaging to human cells.
Visible Light is the portion of the light spectrum which is visible to the human eye, typically 400nm to 780nm.
Table 1, transmittance requirements for Clear Lenses and General-Purpose Filters.
This table provided by ANSI Z87.1-1989 (R-1998)
|Shade Number||Luminous Transmittance Maximum %||Luminous Transmittance Nominal %||Luminous Transmittance Minimum %||Maximum Effective
(1) The near ultraviolet average transmittance shall be less than one-tenth of the luminous transmittance,
_T (NUV)<TL / 10
(2) The blue-light transmittance shall be less than the luminous transmittance.
Optical Radiation Selection Chart
|Application||Protector Type||Filter Shade||Protectors||Limitations||Not Recommended|
|Welding Helmets or Welding Shields||
Protection from optical radiation is
|Protectors that do not
provide protection from
optical radiation. SEE
|Welding Helmets or Welding Face Shields||SEE NOTE (3)|
Spectacles or Welding Face Shields
|SEE NOTE (3)|
|Glare||A,B||SEE NOTE (9) (10)||Spectacles||Shaded or Special Purpose lenses, as suitable, SEE NOTE (8)|
(3) Face shields shall only be worn over primary eye protection.
(4) Filter lenses shall meet the requirements for shade designations in table 1.
(8) Special purpose lenses shall meet all the requirements of the standard except for the transmittance requirements in table 1. They may be used at the discretion of the individual responsible for the safety program.
(9) Welding helmets or hand shields shall be used only over primary eye protection.
(10) Non-side shields spectacles are available for frontal protection only.
A) Spectacle, No Side shield
B) Spectacle, Half Side shield
C) Spectacle, Full Side shield
D) Spectacle, Detachable Side shield
E) Spectacle, Non-Removable Lenses
F) Spectacle, Lift Front
G) Cover Goggle, No Ventilation
H) Cover Goggle, Indirect Ventilation
I) Cover Goggle, Direct Ventilation
J) Cup Goggle, Direct Ventilation
K) Cup Goggle, Indirect Ventilation
L) Spectacle, Headband Temple
M) Cover Welding Goggle, Indirect Ventilation
N) Face Shield
O) Welding Helmet, Hand Held
P) Welding Helmet, Stationary Window
Q) Welding Helmet, Lift Front
¹Z87 13.3 Impact Testing. Lenses shall be capable of resisting the impact of a 25.4mm (1") diameter steel ball dropped from a height of 127cm (50"). The lens shall be tested (un mounted, that is, out of the frame) in accordance with section 15.5.2 and shall not fracture as a result of this test. Prescription lenses, which are likely to experience damage at the point of missile contact in the test above, may be tested using any appropriate protocol. Prescription lenses are exempt from the penetration testing requirements.
¹Z87 13.4 Lens thickness. Lenses made to individual prescriptions shall be not less than 3.0mm (.118") thick, except that those lenses have plus power of 3.00 diopter or greater in the most plus meridian shall have a minimum thickness no less than 2.5mm (.098").
²Information provided by Corning Incorporated