Why does it have a getter

What is a vacuum glazing getter?

We don’t imagine solid materials can allow gas to pass through, but gas permeation is common to all kinds of materials. Under the effect of light and temperature, there will be surface outgassing in any insulated glass unit. This leads to gas molecules passing through the glass and into the cavity to try and equalise pressure and concentrations. A vacuum glazing getter is a reactive material which is put inside the cavity to “mop up” gas particles. By converting these gas particles into inert solids, getters avoid them impacting the effectiveness of the glass unit. Getters are also sometimes referred to as degassers.

Vacuum insulated glass is made up of two panes with an ultra slim cavity in between. This means that the ratio of cavity volume to surface area of glass is very different to typical glass units. As an example, a piece of 1m² vacuum insulated glass has only 150ml of internal air space but a surface area for outgassing of 2m². As baking under high temperature cannot totally eliminate the surface outgassing issues, it is necessary to place getters in the vacuum chamber to improve and maintain the level of vacuum as well as prolong the useful life of VIG units.

What does a vacuum glazing getter do?

A getter raises the integrity of a vacuum chamber quickly and maintains the desired vacuum degree for a long time. There are two types of getters: a vaporized getter and a non-evaporable getter. The vaporized getter, usually a volatile metal, instantly reacts with any residual gas. This then condenses on the cool walls of the tube in a thin coating, the getter spot or getter mirror. This continues to absorb gas; the non-evaporable getter uses a clean approach.  After the material is “activated”, while maintaining its solid form (i.e. Not being evaporated), it turns into the getter that absorbs gas directly.

What does a getter look like?

Getters can come in many different forms and look different in the units of each manufacturer of vacuum glazing. In LandVac, the getter is a small circle located in the corner of the glass unit. This is located in such a way as to be fully concealable in a deep glazing rebate. In AGC FINEO, the getter is a line which runs the full height of the glass unit. Again, this is located close to the edge of the unit to allow it to be hidden in the glazing rebate.

In both LandVac and FINEO, the size of the vacuum glazing getter can change with the overall area of the glass unit. The reason for this is that a greater surface area to cavity volume ratio requires more getter to achieve the same level of performance. In LandVac, this means that in units over 1m2 in size, a second circular getter is required. In FINEO, larger units require a second linear getter along a perpendicular unit edge from the first getter.

The Pilkington Spacia vacuum glazing units did not contain a getter and the impact was a significant reduction in the performance.

For more information on vacuum glazing getters, please contact us.