Witness Samples

Optical witness samples are small, flat glass substrates that are used in the thin film coating process to measure the performance of the coating. They measure the transmission and reflectivity of a given coating design while also providing indicative samples used to quantify the durability and resistance to environmental degradation from the influences of humidity, temperature, and salt exposure. 

One of the main benefits of the Esco Optics witness sample program optimizes prices across large manufacturing runs. For our customers who may only need a small sampling of specialty glass for their coating run, this is a great advantage. A small manufacturing run of 10-15 pieces would be far more expensive than a lot size of 250. Another plus involves the extensive variety of glasses and configurations with a diverse array of choices to cater to varying needs. Catalog witness samples are offered in three configurations, Transmission (polished on both sides), Reflection (polished one side/ground on the opposite) and 8º Wedge.  

Beyond UV fused silica, and specialty glasses, Esco offers IR materials CaF2, ZnSe, Silicon, Germanium which are important for sensing applications, aerospace, defense and more. If you have a unique end-application or market, we can assist with your witness sample requirements. 

Need something that is not part of our standard, catalog offering? We stock Corning, Heraeus, Hoya, Ohara, Schott glass, among others, all with material certifications and data to address your specific needs. Contact our sales team today or get started with an online quote. 

Transmission: Polished 2 sides | Reflection: Polished 1 side/opposite ground finish | IR materials: Polished 2 sides