If you notice a faint line, strip, or row of small marks near the edge of a vacuum glass unit, you may be seeing the sorption getter. (seen below in red on the technical diagram)
That term sounds highly technical, but the concept is actually quite simple.
The sorption getter is a necessary part of the vacuum glass unit. Its job is to help maintain the vacuum inside the glass over time. That vacuum is a major reason vacuum insulated glass performs so well thermally. Without it, the glass would not be able to do the job it is designed to do.
So while it may sometimes be visible, it is not a defect. It is part of how the glass works to hold back 10 tonnes of atmospheric pressure per m2! – Read more about ceramic bridges here
Why does it exist?
Vacuum glass works by creating a vacuum between two panes of glass. That vacuum reduces heat transfer and is what gives the product its impressive thermal performance. We openly share the performance metric differences you get by having these slight compromises – Read more about how the performance stacks up here
The sorption getter is part of that system. It helps support the long term performance of the sealed unit and has to be there as part of the manufacturing design.
In simple terms, it is a functional component of the glass, not an optional extra.
Why can it sometimes be seen?
During the manufacturing process, the getter can appear anywhere within a range of roughly 10mm from the edge of the glass. That means its final position is not always identical from unit to unit.
On larger panes, there can also be multiple getter lines, rather than just one.
This matters because old timber windows generally do not have a large glazing rebate to fully conceal everything at the edge of the unit. In some cases, the getter may sit neatly hidden. In others, it can end up being shown quite clearly as a straight line running against the window rail or stile.
So visibility is not always about something being wrong. Often, it is simply a result of where the getter sits within the unit and the limited rebate space available in an existing timber window.
Why do some windows show it more than others?
Every existing timber window is slightly different, and so is every pane (bespokely made!)
Some old windows are beautifully straight. Others are slightly out of square, bowed, twisted, or irregular from age, movement, and years of service. When that happens, parts of the edge detail can become more visible in some areas than others.
That can sometimes result in sections or strips of the getter appearing, rather than it being evenly hidden or showing around the unit.
This is one of the realities of retrofitting modern high performance glass into old timber windows. We are working within the existing frame, not manufacturing a brand new window around the glass.
In comparison, standard performance double-glazing units (Sealasash do not install these) show a very large black rubber edge around the perimeter (see below).
Glavenir by Panasonic offers an exceptionally fine edge seal by vacuum glass standards and is, in our opinion, best in class in this space. For customers who want the highest level of thermal performance, it is an outstanding option. For customers who place a higher priority on a cleaner visual outcome, lower performing alternatives such as 4mm low e Energy Tech or 6.38 laminated Comfort Plus glass can sometimes provide a more discreet finish.
Why can’t it just be removed or fully hidden?
Because it has to be there.
We do not manufacture the vacuum glass unit itself – Panasonic do, and the getter is part of that product’s construction. It cannot simply be removed without affecting the design and function of the glass.
We always do our best to set the glass as neatly as possible and minimise visibility wherever we can. But there are limits, especially in older timber windows where rebate depth, frame shape, and natural irregularities all play a role.
In some cases, the getter will be mostly hidden. In others, it may be partially visible. Occasionally, it may show quite clearly as a straight line along one edge.
Our approach at Sealasash
At Sealasash, we do the best we can to achieve the neatest possible finish while still respecting the reality of the product and the existing window.
We carefully retrofit the glass into old timber frames, but we do not manufacture the vacuum glass units themselves. Some parts of those units must remain exactly as designed in order for the glass to perform properly.
That means the getter is a necessary part of the system, and in some windows it may be visible due to manufacturing position, pane size, rebate limitations, or the irregular nature of older timber frames.
The simple version
The sorption getter:
- is a required part of vacuum glass
- helps the unit maintain the vacuum that gives it its performance
- can sit within about 10mm of the glass edge depending on manufacturing
- may appear as one line or multiple lines on larger panes – generally appears on the longest side.
- can sometimes be visible because old timber windows often do not have enough rebate depth to fully hide it
- may show more in windows that are out of square, bowed, or irregular
- cannot simply be removed
- is something we always try to keep as discreet as possible
Other important information about vacuum glass you should know
At Sealasash, we do our best on site to explain as much as possible within a set amount of time. That said, vacuum glass is a highly specialised product, and sometimes not every detail can be fully covered during a consultation, measure, or installation discussion.
If you are considering vacuum glass, or already have it installed, the resources below may help you better understand how the product works, why it looks the way it does, and where it may or may not be the right fit.
Ceramic bridges
These are the tiny support structures inside vacuum glass that help keep the panes separated under vacuum. Learn more here:
What’s a vacuum and what are the black dots?
Black dots vs translucent dots
Not all vacuum glass products look the same. This article explains why some products use ‘translucent’ micro pillars, while Glavenir by Panasonic takes a different approach:
Translucent vacuum glass vs black micro pillars – why Glavenir doesn’t need to hide its dots
Australia’s supplier of Glavenir by Panasonic
Vac Glass Australia is the Australian supply arm for this product and a trading arm of Sealasash:
Vac Glass Australia
Lead light and heritage applications
Vacuum glass can also work with lead light windows in certain applications. Learn more here:
A new solution: double glazing lead light
Sound reduction performance
Vacuum glass is not just about thermal comfort. It can also offer excellent acoustic benefits depending on the specification:
Cutting edge soundproofing
Overall product specifications
For those who want a deeper technical overview, you can view the general product specifications here:
Product specifications
or view the Panasonic Glavenir spec sheet directly here:
6.1mm and 8.1mm Glavenir spec sheet
A simple explanation from our Business Development Manager
Sometimes it is easier to see and hear it explained. This short video gives a straightforward overview of vacuum glass and some of the details that can come with it.
