The Good, The Bad, and the Better: Alloys and Non-Alloys in the Lab

By Christie Walker
When it comes to thermo-reactive blocking media, alloy has been the most -stable and widely used for surfacing in the -optical industry. There have always been advantages and disadvantages to using alloy, but up until recently, optical laboratories haven’t had many viable alternatives to alloy blocks. LabTalk has asked three companies to give us the good, the bad and the better about alloy and alloy alternatives for lens processing.

The Good

Up until now, alloy has been the most stable of the thermo-reactive blocking medium available for surfacing, which is why it has endured for so long. All of the other products in the market have brought compromises to the process. In addition, alloy has been the only product able to successfully block prism, a technique that has proven to be essential for producing the newer digital designs. A final advantage is alloy’s compatibility with the AR process. Ian Gregg, Satisloh.

Alloy has been in and out of the industry over the past 20 years. As an industry we recognize it contains hazardous substances and to a certain extent, understand that the handling and disposal of alloy should be a concern. Although the production demand for free-form lenses and a trend into larger and more powerful lens generators has pushed many users back into a dependence on alloy products, we need to know the true -hazards involved in the use of alloy, specifically the -high-risk -substances within alloy including lead, cadmium and indium. Curt Brey, Coburn Technologies

Alloy is a great material for what we do in terms of mechanics. It melts at a low temperature and hardens at high temperature. It’s a rigid and strong support for the high-dynamic forces of surfacing. Alloy is almost the perfect medium for what we do. In addition to relative ease-of-use, it provides a great support for the lens and does not flex or change geometry—critical for surfacing of lenses. Kurt Atchison, Schneider Optical Machines

The Bad

Of course, the positive mechanical properties of alloy come at a price—environmental concerns. While with proper care and handling, labs can alleviate those concerns (use of gloves, filtration of alloy-touched fluids, -filtering alloy out of waste stream, etc.). Labs are also looking to eliminate the need for the extra steps necessary to work with alloy. It seems clear that the requirements for reducing use of lead and other alloy components will only grow stricter in the future. The other negative side of using alloy is the price. Alloy is generally expensive and subject to large fluctuations in price that are not predictable for the lab long term. Kurt Atchison, Schneider Optical Machines

Mostly what’s bad about alloy is its use of lead, cadmium and indium to make the product work for lens processing. While there are “lead and cadmium free” alloy products available, they often contain over 50 percent of indium as a substitute. It is always good to get out of using lead and cadmium however, indium is registered as just as hazardous a substance as cadmium, so the actual benefit is minimal at best. The greater concern overall is handling of the product in the lens manufacturing process such as: operator contact with alloy-blocked lenses; debris from generating and deblocking; spilled alloy on work tables, tools, clothing; and other contact surfaces. Also bad are the fumes released when alloy is melted in deblocking tanks as lead, cadmium and indium have a different resulting impact through physical contact versus inhaling the fumes from melting the substances.

The reality is that agencies in the U.S. and E.U. have -either banned or set strict management policy for lead, cadmium and indium in most major industries where the substances are used. The ophthalmic industry seems to have slipped under the radar for most restrictions but that doesn’t make the product any less hazardous or -dangerous for the work force of the ophthalmic lens processing industry.

Coburn has recently researched what the national U.S. and E.U. health and safety agencies have to say about these hazardous materials and their impact on those people that work in lab environments that use alloy. Coburn’s research included not only observational and field study, but also 18 published documents and reports on the topic from eight different U.S. and E.U. agencies and national teams including the EPA, OSHA and the CDC. Following this research study, Coburn has discontinued all of its alloy products. Curt Brey, Coburn Technologies

As with all thermo-reactive products, it inevitably introduces heat into the lens being blocked. This requires the lens to “cure” for a minimum of 30 to 40 minutes prior to generating and even then there remains the possibility of lens spoilage due to excessive heat, particularly with high-index products.

All lens materials must have surface saver tape applied prior to the blocking process, an additional step in the process requiring additional consumable product and labor costs. The most common type of alloy used in a lab contains several extremely hazardous elements including cadmium, which make it difficult to handle and dispose of safely. There is a cadmium-free version available, but it has a much higher melting point (see drawback number one) and is therefore mostly limited to the production of mineral glass. In addition to cadmium, alloy contains several trace elements that are used in other industries (plasma screen TVs for example) that are extremely price volatile. The result is that alloy is sold as a commodity that can be speculated on resulting in pretty dramatic price swings for the product. Ian Gregg, Satisloh

The Better

Satisloh’s Nucleo

Our newest technology, known as Nucleo, leverages a completely new blocking technique. Using a clear plastic block piece and UV cured adhesive, this blocking system offers all the advantages of alloy (stable, predictable process characteristics, prism blocking, and compatibility with the AR process) with none of the drawbacks associated with alloy and thermo-reactive products in general. It does not introduce heat into the lens material, which means the lens can go directly to generating without excessive curing time. The plastic block is made from a common, recyclable material and the adhesive once cured is completely inert. In addition, no taping is required thus eliminating a non value-added step in the process.

Why It’s Better

Of course the big win with the Nucleo technology is OBM, or On Block Manufacturing. Once the lens has been blocked, it can be processed through the entire lab including spin coating, AR coating and edging, while remaining on that same block. The result is fewer process steps and a higher level of automation than had previously been possible. Coburn Technologies’ OnyxBond

The growing demand of free-form lens processing and AR coating in the U.S. inspired Coburn to develop not only a new blocking system called the E2G Surface Blocking System but more importantly, an entirely new blocking material called OnyxBond. OnyxBond is a powerful non-alloy blocking material that is completely safe, easily recycled, affordable, user-friendly, fast and accurate. Made from components including FDA-approved products from the dental industry, OnyxBond isn’t just different than alloy, it’s better for every lens processing application from free-form, to conventional, to specials. Why It’s better?

The E2G and OnyxBond eliminate the risks and waste caused by alloy in the lab. Operators who use and handle OnyxBond don’t need to worry and owners don’t need to be concerned about the risks of alloy for their people or their business. OnyxBond is simply a better blocking compound for lens processing, especially free-form lens processing. It’s non-toxic, less expensive, wax-free, AR compatible, machine-able, and it’s completely proven in labs world-wide. Furthermore, it offers the fastest and cleanest deblocking process in the world.

Schneider Optical Machine’s Connex

Schneider’s new non-alloy material, Connex, solves all the above problems of alloy and meets the requirements of a new blocking medium for processing ophthalmic lenses. In addition to environmental and cost solutions, it also provides the same benefits mechanically of alloy. That is, it’s a very rigid material that provides a firm foundation for the high dynamics of modern surfacing and can cover the entire lens surface for even greater support at the lens edge.

Why It’s better?

The Connex solution solves all the environmental, mechanical stability, and cost issues involved in a product needed to replace alloy. In addition, this new material allows us to exchange alloy or other blocking systems seamlessly as “alloy replacement.” The key for Schneider is to provide a low cost solution that can remove alloy but without a significant reorganization of other lab steps. We are striving for a simple switch: alloy blocker out, Connex blocker in. If we can make this switch, the benefits above are all realized but existing production lines are only positively effected.

Advantages to Switching

New blocking materials will be cheaper. Our target cost-per-lens for non-alloy blocking is a fraction of alloy. And the costs will be predictable because the price won’t fluctuate like they do with alloy. But more importantly, the new material will be completely safe and free of any environmental concerns. This eliminates special handling requirements as well as any health risks believed to be possible with alloy. Kurt Atchison, Schneider Optical Machines.

The switch from alloy to a non-alloy blocking product needs to move a lab forward not backward. The switch needs to enhance the operation and profitability of the lab, replacing all applications of the alloy product without compromising the process or limiting what the lab can produce. It’s great to make a change to keep the work force safe and healthy but even better when you improve business because of it. Advantages of switching from alloy to non-alloy will include less costly blocking material, reduced risk in insurance costs, waste management costs, environmental pollution, and overall business risk. Health insurance costs aren’t getting any lower in the U.S. and the risk of work-related illness and injury compound that expense for any business. Continuing with the use of alloy only increases the risk that businesses will face going forward, something every business should address sooner rather than later. Curt Brey, Coburn Technologies


Labtalk June 2020