The glass used in a lightboard should be low-iron, which is known as ultra-clear glass. Starphire™ is one specific brand of ultra-clear glass, though there are many others. Low-iron glass has greater optical clarity, allowing edge lights to illuminate writing across the board evenly. Standard (non-low-iron) glass has lower clarity so less light is able to penetrate through to the center of the glass sheet. This negatively results in noticeably brighter glowing writing near the edges of the glass than in the middle. For strength and safety we use tempered glass in our lightboards.
Occasionally plexiglass (acrylic) has been used for self-built lightboards but should be limited to proof of concept or temporary builds as these materials scratch very easily and these scratches are very noticeable with internal lighting. This quickly becomes unpalatable.
Many users have built lightboards using our DIY component kits and ultra-clear glass they’ve purchased locally using the specifications and dimensions we provide. Purchasing a clear piece of glass can be challenging and is often the most frustrating step of the entire build. By and large, customers are able to get results they can accept, but there can be hurdles along the way.
When buying their own glass locally, 25-30% of our customers return their first piece of glass due concerning visible marks. Typically vendors are helpful in replacing the glass with another piece but, in some cases, it takes a few rounds or multiple vendors.
Tempered glass has about 4 times the strength of regular glass and, if broken, it will crumble into small pebbles to avoid the danger of large sharp pieces. For these reasons our lightboard glass is tempered to ASTM C1048 standards.
When glass is tempered, it enters a hot oven on rollers where it rolls back and forth to allow even heating and prevent distortion. After the heating cycle, the hot sheet of glass exits the oven and is air-quenched to rapidly cool the surface and produce the differential stresses that give tempered glass its strength and safety properties. Throughout the process, the hot glass is traveling over steel rollers with a heat resistant fabric wrap. Based on the texture of this wrap and the possible presence of glass dust, often a haze or “ghosting” is produced on the large face of the glass which becomes visible when internally lighting the glass. This is typically most prominent in the center of the glass sheet and can resemble a large "Milky Way" pattern with prominent wavy lines.
We extensively polish our lightboard glass to remove about 95% of this haze. What remains isn't able to be seen by the camera with proper settings. Below are some pictures that show a piece of glass before and after our polishing process.
Keep in mind that for inspection we intentionally use high internal lighting and work in an otherwise dark room for best visibility. The piece shown on the left has about double the tempering haze of an average piece. Below is a photo a customer with a DIY kit based system sent us where you can see some light haze on the lower left part of the glass and this was a far better than average piece. If being very discriminating, they could see a little bit of that in the video image. Camera settings can do a fair amount to minimize visibility of the tempering haze but often not entirely eliminate it. Visible haze and wavy patterns can also be discomforting to presenters.
Given the internal lighting of the glass, lightboards are particularly sensitive to scratches and surface rubs. The quality requirements are considered borderline extreme by glass plants and suppliers. Small defects that would normally never be seen in most applications are suddenly illuminated by the internal lighting and become very visible. Scratches and other surface rubs can result from manufacturing, transportation, and handling along the way. Again, our polishing process is able to remove the vast majority of these defects down to a low level where they’re not detectable by a camera with proper settings.
By nature, glass has small air bubbles and other irregularities and there is no practical way to entirely eliminate these though industry standards govern the allowable size and frequency to a reasonable level. Air bubbles can create a "bright pixel" in the video though there are simple ways to reduce this like putting a small black dot on the camera side of the glass if there is a noticeable bubble. Typically that's not needed.
All Revolution Lightboard glass is extensively polished in-house to provide consistently high quality to the end users. This is a laborious process, to say the least, but it is part of what separates the quality of our complete lightboard systems above all others.