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Understanding Glass Parallelism

Parallelism as a parameter plays a crucial role in glass fabrication. As it pertains to glass, the back and front planes of a glass part would achieve parallelism if the space between the planes remained the same so that they run alongside each other but never touch. However, parallelism in actuality is not perfectly possible for glass parts, which is why a parallelism conversion tool or calculator can help measure accuracy for setting any necessary limits.

Defining Glass Parallelism

Glass parallelism, also termed glass wedge, can be determined through various measurements, including transmitted wavefront error (TWE), total thickness variation (TTV), and arcs (minutes and seconds). TWE is the amount of deviation in degrees observed in a wavefront due to beam transmission through an optical device. Parallelism, energy, and irregularity can all directly affect the total wavefront error.

TTV is the value of the difference from the maximum to minimum thickness values over a part’s clear aperture. An interferometer and a scan pattern can help define the value to within 0.1µm and therefore successfully manage a thickness variation of less than 1µm. 

An arcminute is an angular measurement standard unit equivalent to 1/60 of a single degree while an arcsecond is equal to 1/60 of 1 arcminute, or 1/3600 degrees of a circle. Both minutes and seconds of arcs can translate, in degrees, to the amount that they deviate from full parallelism. Parallelism calculators can help you determine the definition of glass parallelism in surfaces to get an accurate measurement, which you can use to develop optical wedges.

Glass Parallelism Calculation Diagram

Applications for Optical Wedges

An optical wedge is fabricated to possess a minimal angle between two glass planes or surfaces and refract or deflect light at that predetermined angle when it hits the wedge surface. The angle could represent only a fraction of a degree, approaching true glass parallelism, to as much as a 3° angle. Even though high-precision optics are usually lapped and polished to achieve near-perfect parallelism, most will still have a slight optical wedge that measures in seconds or minutes of arc. 

Optical wedges come in different shapes and sizes, have different tolerances or coatings, and are mainly designed to change the direction of light and prevent reflections. Many industries have adopted optical wedges for applications such as:

  •     Beam steering
  •     Beam shaping
  •     Machine vision
  •     Telescopes

Optical Glass From Swift Glass

At Swift Glass, we provide comprehensive, precise optical glass fabrication services for projects that require large production runs in little time, without sacrificing quality as an ISO- and ITAR-certified company. Optimal performance is key in optical glass parts like lenses and optical windows, so we carefully consider the chemical and mechanical properties of the glass in addition to the optical factors like surface flatness, quality, and finish.

Swift Glass focuses on the proper levels of glass density, transparency, and purity. Our laser and imaging systems allow us to offer scratch-dig specifications to 40-20 in a variety of sizes, and in some specific instances, a scratch-dig of 20-10 is achievable. We also offer a selection of materials and color filters for customization.

Swift Glass has a newly created parallelism calculator to help with the conversion of degrees to arcminutes and arcseconds to best serve our customers. To learn more about our capabilities for optical glass or this conversion tool, contact us today or request a quote.

6 Key Behaviors of Light on Glass

Light has different properties that affect how we visualize objects. When waves encounter various barriers and mediums, like water, steel, or glass, they behave in different ways. Here, the team at Swift Glass shares the unique behaviors of light on glass. 

Properties of Light

Light is a form of energy and part of a wider spectrum of electromagnetic radiation from the sun. Wavelengths tell us what type of light we’re dealing with. For example, microwaves and radio waves are on the long side of the spectrum, while UV rays and X-rays are much shorter.

When light hits an object, it may be absorbed, reflected, or refracted, depending on the type and shape of the material it hits. This is a key consideration when designing lenses, which are optical devices that use refraction to focus or disperse light. When creating lenses for microscopes, cameras, eyeglasses, and more, engineers have to consider the properties of the material and how light will interact with it.

Behaviors of Light

Light waves and particles interact with glass and other materials in different ways, depending on the type of light and the structure of the material:transmission

  • Transmission: The light passes directly through without being reflected, scattered, or absorbed. A transparent material, like a typical window, allows transmission of almost all light. An opaque material allows no transmission at all, and a translucent material, like a shower door, allows some transmission—however, that light gets scattered, which results in an unclear picture of what’s behind that translucent glass. 
  • Reflection: All types of waves, including light and sound, reflect off certain materials. When it comes to sound, certain animals, like bats, use that reflection (echoes) to find their way around. When it comes to light, smooth surfaces reflect it best: the perfect smoothness of a mirror gives us a clear reflected image, while the moving surface of the water gives us a blurry reflection. Reflection is also how we see color: a purple object, for example, is absorbing most of the wavelengths and reflecting the one we see as purple. 
  • Refraction: Light travels at different speeds through different mediums, and passing from one medium to another changes the direction of the light (refraction) and typically causes it to change speed. The bending of light through a convex lens can make objects appear larger. 
  • Diffraction: This is the bending and the spreading of the light waves—it’s what causes rainbows! You can also diffract light on purpose using a spectrometer to separate the wavelengths. This is useful in scientific applications to measure specific types of light.
  • Absorption: When light photons hit the atoms and molecules that make up the highway, for example, those atoms vibrate and create heat. Dark materials (like a blackhighway) absorb more than light-colored materials (like the gray sidewalk)—which is why you may tend to prefer wearing a white shirt instead of a black shirt on a hot summer day.scattering diagram
  • Scattering: This is when light bounces off the glass in multiple directions. There can be a little scattering or a lot, depending on which type of wave is scattering and what type of object it’s scattering off and through. This is why the sky is blue: nitrogen and oxygen scatter the short blue and violet waves, while the longer red and yellow waves pass right through. Violet waves are actually shorter and scatter more than the blue ones, but our eyes are more sensitive to blue, so that’s what we see when we look up on a clear day. 

The way light behaves is fascinating, which is what makes the optical industry so exciting. Learn more about light and its properties and behaviors, or contact us for more information about custom glass fabrication. Swift Glass is a worldwide leader in high-quality glass manufacturing, and our experienced team works to ensure we meet your specifications and expectations as well as industry standards. We work on projects in a range of industries and applications. Request a quote today. 

Microblasting vs. Sandblasting

At Swift Glass, we specialize in the fabrication of quality glass components. We offer a range of fabrication capabilities to ensure the parts and products we deliver fully meet our customers’ specifications and standards. For example, our machining and surface finishing services allow us to carefully alter the shape and/or surface of very small to very large glass materials.

Two commonly utilized machining and surface finishing processes are microblasting and sandblasting. While these processes might seem similar at first glance, they use different tools to achieve different results. Below, we provide an overview of both processes and highlight some of the key differences between them.

What Is Microblasting?

Microblasting—also referred to as microblast machining or micro-abrasive blasting—is a fabrication process that utilizes fine abrasive media and small nozzles to generate an accurate, precise, and controllable abrasive jet. The jet can be used to target and remove material (on the micron level) from a workpiece for various purposes. For example, it can cut glass into various shapes and sizes, create small structural elements (e.g., holes), produce fine surface textures, or clean/strip the workpiece surface in preparation for subsequent processes.

Due to its versatility, microblasting finds application in many industries. For example: Electronic circuit board close up.

  • In the medical industry, it is used to remove excess or residual material from manufacturing tools (e.g., molds) and manufactured components (e.g., implants).
  • In the aerospace industry, it is used to clean off residues from components such as circuit boards and create surface textures on components such as connectors and HUD optics.
  • In the electronics industry, it is used on electronic components to cut holes for easier assembly and create textures for improved bond adhesion.

What Is Sandblasting?

While the sandblasting process is based on similar principles as the microblasting process—i.e., using compressed air to force abrasive media out of a nozzle at high pressures and speeds—it is generally used for different reasons. When the abrasive media hits the glass, it produces microscope scratches. These scratches are used to achieve a specific texture for functional or aesthetic purposes, depending on the intended application of the final component.

In contrast to microblasting, sandblasting is typically reserved for cutting and texturing applications. Typical uses include:

  • Carved glass components
  • Frosted glass components

Microblasting vs. Sandblasting

Microblasting vs. Sandblasting Infographic

Click to Enlarge

Both microblasting and sandblasting can be used to shape and texture glass by blasting abrasive media at high speeds across the surface. However, each has unique capabilities that make it better suited for particular applications.

Advantages of Microblasting

Microblasting is a more versatile process. It can cut, drill, smooth/roughen, and clean/strip glass surfaces. It is also more precise and accurate, removing material down to the micron level to produce high-quality finishes.

Advantages of Sandblasting

Sandblasting uses larger abrasive media and nozzles, making it less accurate, precise, and controllable than microblasting. The advantage is that it can quickly process large glass surfaces while still achieving good quality finishes.

Microblasting Services at Swift Glass

Want to learn more about microblasting and sandblasting? Ask the glass fabrication experts at Swift Glass! We maintain advanced microblasting capabilities as well as sandblasting capabilities to produce quality glass components for our customers. If you have a question or concern about either process, we can answer or address it. For all of your glass machining and/or finishing needs, request a quote to discuss your specifications and standards.


Understanding the Refractive Index of Glass

Understanding the behavior of light can be an important factor when determining which glass materials to use for your manufacturing process. When light passes through a substance, it decreases in velocity. This is manifested by an increase in the substance’s refractive index. Much can be learned about the optical properties of a glass material by looking at its refractive index.

Refractive index is useful for various reasons. For one thing, it can be used to calculate the focusing power of lenses and the dispersive power of prisms. It can also be used in estimating the thermophysical properties of hydrocarbons and petroleum mixtures.

What is the Refractive Index?

Also commonly referred to as the index of refraction, the refractive index, n, measures a ray of light as it travels from one medium to another. As it begins to travel through a material, the interaction between electrons and photons reduces the speed of light. As the density of the electrons increase, the velocity of light becomes slower.  This is why light moves at its highest possible speed in a vacuum, where no electrons hamper its speed.

Knowing the refractive index – among other thermal, chemical and physical properties – helps ensure that the glass material you’re considering for your application is suitable for its intended use.

Determining the Refractive Index of a Material

The ratio between the speed of light in a vacuum and the lower velocity of the light as it travels through a given material enables us to determine the refractive index of a given material.

In addition, the amounts of transmitted and reflected light will determine not only the refractive index of a glass material, but also its angle of refraction. This is because light gets transmitted and reflected as light rays pass through the surface of a glass material.

The light’s transmission angle can be calculated using Snell’s law:

The discrepancy between the light’s transmission and the incidence angle becomes bigger as the index of refraction becomes larger. When this occurs, there is a change in the existing refractive index between the glass and the surrounding medium.

When Θi = 0°, the amount of reflected light can be determined using the following formula:

Lastly, the intensity of light is reduced by an average of 4% due to lost reflection from the surface of most glass materials with a 1.5 refractive index.

A change in the index of refraction due to changes in wavelength is known as chromatic dispersion.


Swift Glass has been providing custom glass manufacturing services for nearly a century, and providing high-quality solutions to OEMs is one of our core principles. Our experience and dedication to customer service enables us to understand the intricate needs of our customers, and to exceed their basic needs.

An ITAR registered, ISO 9001:2015 certified company, Swift Glass is a privately-owned global leader in the quality fabricated glass parts. Swift Glass offers assistance in craftsmanship, material selection, and manufacturing of custom solutions, and design, while guaranteeing high quality and precision.

To learn more about the optical properties of glass, download our latest eBook, Understanding the Optical Properties of Glass today!

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Swift Glass to Attend Photonics West 2017 Exhibition

Swift Glass is excited to announce that we’ll once again be attending the annual SPIE Photonics West Conference and Exhibition, at the Moscone Center in San Francisco from January 28 to February 2.


Hosted by the International Society for Optical Engineering (SPIE), Photonics West has been the world’s largest multidisciplinary event for biomedical and medical photonic technologies for over two decades. Attended by over 20,000 people, this exhibition draws industry leaders from across the country to view new technologies, hear educational speakers, and network with others in the field.

State-of-the-art medical devices and systems, the Internet of things, smart manufacturing and “Industry 4.0” autonomous vehicles, communications equipment, new scientific research, and various displays will all be on view at the photonics exhibition. Attendees will have the chance to go to technical and networking events, as well as professional development seminars and student events. Various workshops will also be offered, with topics including laser applications, optomechanics, semiconductor lasers and LEDs, and biomedical spectroscopy, miscopy, and imaging.

We’ll be set up in Booth #608, displaying various types of display glass, as well as large chemically strengthened rectangular glass and other samples of our chemically strengthened glass. We’re looking forward to speaking with other optics conference attendees and showcasing our unique product line. We hope to see you there!

As an ISO-certified and ITAR-registered company, Swift Glass is committed to quality in everything we do. Our custom glass manufacturing capabilities include chemical strengthening, waterjet cutting, edge grinding, thermal tempering, surface lapping, CNC machining, polishing, drilling, and optical glass fabrication.

To learn more about this exciting glass manufacturing conference, reach out to us today. And, for more information about our diverse service offerings, visit our website.

Thermal Glass Tempering vs. Chemical Strengthening: What’s the Difference?

Glass Solutions for Extreme Environments

Glass is among the world’s most sophisticated materials. Specialty glass can withstand high pressure, extreme heat, and extraordinary environments.

There are two primary methods for strengthening glass: chemical strengthening and thermal tempering. Both of these processes alter the outer surface of the glass, causing it to have a higher compression than the interior glass, which is in a state of tension. Depending upon the specific application, each process offers unique advantages for a material’s final makeup.

Chemical Strengthening

thermal-tempering-500x370Also known as ion exchange, chemical strengthening treats glass by submerging it in a molten potassium salt bath, causing sodium ions in the glass to be replaced by potassium ions from the bath. The potassium ions, which are larger than the sodium ions, squeeze themselves into the gaps left by the smaller sodium ions when migrating to the potassium solution. The surface of the glass is then in a state of compression while the core is in compensating tension.

The chemical composition of the bath can vary widely, allowing this process to be tailored to the material’s final application.

Chemical strengthening can create a high-performance glass with no notable distortion and a very shallow surface layer of strengthened, alkali-rich material. The added strength of this specialized glass makes it ideal not only for harsh environments but also for high-performance applications in conductors, semiconductors, energy, medicine, and more. Chemical Strengthening can be performed on much thinner glass than heat tempering.

Glass Tempering

safety-glassTempered glass undergoes an intense heating process immediately followed by rapid cooling. This extreme temperature shift causes the glass surface and edges to compress, creating an extremely tough outer surface with a tensioned glass core.

When broken, tempered glass breaks into small particles along circular edges, eliminating the risk of dangerous shards. This makes tempered glass an ideal choice for a wide range of applications, including:

  • Industrial environments
  • Safety glass (windshields, windows, and situations with exposure to projectiles)
  • High-temperature environments and thermal stresses
  • High-pressure applications

From aviation and aerospace to laboratories and industry to household items and fire safety, both chemically strengthened and thermally tempered glass offer countless solutions to daily safety and environmental challenges.

Glass Solutions from Swift Glass

extreme-environmentsNo matter the size or demands of your project, Swift Glass can help. Our specialists offer ultra-high pressure cold cutting, CNC machining, polishing, drilling, printing, and a host of other manufacturing capabilities to support both our chemical strengthening and thermal tempering services.

To learn more about high-performance glass that can withstand even the most difficult circumstances, download our new eBook, Creating Glass That Withstands Extreme Environments, or reach out to us today!

Glass vs. Plastic: Which Is Best for Your Next Project?

When choosing between glass and plastic for an application, many people with cost-conscious applications expect plastics to be the cost-effective choice. But you just may have more options than you think.

In the long term, plastic can actually accrue higher costs in maintenance, replacements, and repair work. Both materials offer specialized benefits in a wide range of applications, but the perks of glass offer long-term benefits and unexpected savings.

Low Maintenance, High Performance

Sheets of Factory manufacturing tempered clear float glass panels cut to sizeGlass promises superior overall performance when compared to plastic: better transmittance, improved insulation, and high scratch resistance are just the beginning. Customers choose glass for its high-end aesthetics, weather and chemical resistance, and low expansion and contraction in extreme temperatures.

But it’s more than just a higher level of performance — glass offers durability, meaning lower costs for maintenance. Less frequent repairs and replacements also mean less cost in the long-term, not to mention less stress.

Versatility Without Compromise

The resilience of glass, as well as its wide variety of treatments and formulations, allows it to outperform plastic in countless cost-effective applications across industries, including:

Cost Effective Performance at Swift Glass

price-of-glass-coverThe Swift Glass team stands ready to help every customer find the best glass material fit — and still save money. We focus on procuring the ideal material investment for a project, and we’re proud to maintain a vast inventory of glass variations to suit any project, performance challenge, or price point.

Learn more about what affects the price of your glass parts with our new eBook, or contact us today!


3 Reasons to Use Waterjet Cutting

A waterjet’s small stream size and controlled pressure makes it the ideal choice for cutting many materials. From shaped mirrors to cell phone panels to very thick materials, waterjet cutting is the go-to method for a variety of industry applications.

Here are three reasons why manufacturers choose waterjet cutting for their projectswaterjet_closeup_large

Smoother Cutting

A water jet cutter’s highly pressurized stream of water — sometimes cut with garnet or aluminum oxide as the abrasive — provides an exceptionally smooth and controllable tool. Controlling the speed of cutting allows thin or thick glass or ceramic to be smoothly cut very economically.

Etched, taped, and coated surfaces are safe for waterjet cutting, too.

Superior Precision

Regardless of the shape, size or specific glass material, our omni-directional jet stream can cut almost all shapes down to 0.1mm in thickness. The high pressure generated from the machine’s water pump creates pinpoint accuracy to smoothly cut holes, notches and details without distortion.

This kind of precision makes waterjet cutting optimal for applications in all types of industries — automotive, lighting, architecture, energy, marine, medical, aviation, and more.

High Performance for Thick Materials

A wide variety of glass products benefit from water jet cutting, from ultra-thin smartphone panels to thick multi-layered bullet-proof vehicle and building panels to delicate stained glass windows. As the thickness of glass increases, waterjet cutting offers superior speed and accuracy, even for materials like explosion-proof glass.

The Swift Glass Team offers precision cutting for glass and ceramic up to several inches thick. Some other applications for waterjet-cut glass, both thick and thin, include:

  • Ornamental Components
  • Solar Panels
  • Gauges
  • Wafers
  • Wood burning stoves

With more than twenty years of experience in water jet cutting, the Swift Glass team can confidently recommend its versatility and precision for your next project. We work with the latest cutting technology to accommodate even the most complicated projects.

Find more information and specifications on water jet glass cutting and other services at Swift including our capabilities at swiftglass.com, or contact The Team with questions about your project today.

Are You Asking Your Glass Manufacturer the Right Questions? The Swift Glass Team Can Help

Eighty years of business adds up to a lot of projects, and that means a lot of questions. Our team is experienced, available, and happy to help — but do you know what to ask them?

Over time, we’ve paid attention to the most common questions that come up in glass manufacturing, and thought we’d give you a head start on your next project. We’ve found that these are the most important points to consider in order to ensure every client selects exactly what is needed.5-questions-to-ask-cover


What temperature and pressure ranges can your materials handle?

It’s important to consider every facet of your design’s projected performance and exposure before selecting a material. Manufacturers like Swift Glass keep an immense inventory, with both raw materials and ready-made products available. This wide range of choices means that it’s more likely we’ll have the perfect glass in stock to meet your desired temperature and pressure ranges.

Having these materials at the ready means a product’s turnaround time is far more efficient. However, this isn’t a place to rush! Carefully evaluate the qualities you need, including:

  • Thickness
  • Normal Service Temperatures
  • Extreme Service Temperatures
  • Maximum Temperature, Thermal Shock
  • Maximum Temperature, Thermal Gradient
  • In/In/ oF Coefficient of Thermal Expansion

We carry Float, Pyrex®, Borofloat®, Quartz and Vycor®, covering nearly any high temperature or pressure application. Once you’ve determined your project’s range, check out our website, eBook resources, or call the team for material-specific details and reference charts.


What is the difference between tempered and non-tempered glass?

Once glass is machined to final size, it may stay as annealed or it can be tempered in a heat treatment process. This process heats the glass above the strain point; then rapidly cools the glass- putting the surfaces in compression. Doing this operation increases the resistance to thermal shock as well as making the glass able to withstand up to 4 times the amount of pressure compared to un-tempered glass.

Find more details about tempered glass with our full response in the new eBook, 5 Important Questions to Ask Your Glass Manufacturer. You’ll find detailed answers to the questions highlighted here, as well as three more common questions:

  • How quickly can my project be completed?
  • How can we reduce our project’s costs?
  • What is the vendor’s production volume?

These are our most common questions, and they’re a great place to start! Find the whole eBook here on our website, or contact the team with your own questions today.


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