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

 

X-Ray

 

General Information

 

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 Glass;
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.

 

Welding Shades
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 Far-UV Average Transmittance	Maximum Infrared Average Transmittance
Clear	100	---	85	---	---
1.5	67	61.5	55	0.1	25
1.7	55	50.1	43	0.1	20
2.0	43	37.3	29	0.1	15
2.5	29	22.8	18	0.1	12
3.0	18.0	13.9	8.50	0.07	9.0
4	8.5	5.18	3.16	0.04	5.0
5	3.16	1.93	1.18	0.02	2.5
6	1.18	0.72	0.44	0.01	1.5
7	0.44	0.27	0.164	0.007	1.3
8	0.164	0.100	0.061	0.004	1.0
9	0.061	0.037	0.023	0.002	0.8
10	0.023	0.0139	0.0085	0.001	0.6
11	0.0085	0.0052	0.0032	0.0007	0.5
12	0.0032	0.0019	0.0012	0.0004	.05
13	0.0012	0.00072	0.00044	0.0002	0.4
14	0.00044	0.00027	0.00016	0.0001	0.3

 

Notes:

(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.

TB<TL

 

Optical Radiation Selection Chart

 

Application	Protector Type	Filter Shade	Protectors	Limitations	Not Recommended
Welding: Electric Arc	O,P,Q	SEE NOTE(9) 10-14	Welding Helmets or Welding Shields	Protection from optical radiation is directly related to filter lens density. SEE NOTE (4) Select the darkest shade that allows adequate task performance.	Protectors that do not provide protection from optical radiation. SEE NOTE (4)
Welding: Gas Cutting Torch Brazing	J,K,L,M, N,O,P,Q	SEE NOTE(9) 4-8 3-6 3-4	Welding Helmets or Welding Face Shields	SEE NOTE (3)
Torch Soldering	B,C,D E,F,N	1.5-3	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)

 

Notes:
(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.

 

Protective Devices:

 

 

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