As someone with over 30 years of experience manufacturing sealed units, I can’t think of another time where the heritage sector has been so firmly in the industry spotlight. Whether it’s best practice, compliance or consolidation, there are a multitude of issues which have ultimately got the industry talking.

I fear though, we could be facing another potential issue, with a number of reported unit failures recently due to glazing methods not being followed. In this case, it involves compatibility issues between the paint used and the glazing method chosen, as well as painting heritage units before the putty compound has cured effectively. Either way, this is undoubtedly one of the biggest causes of unit failure, yet it is so easily avoidable.

In an effort to encourage best practice and to support our customers, we have spoken at length with our supply partner Hodgson Sealants to determine the best ways to glaze our Slenderline units when different paint types are being used. For those using water-based paint, Hodgson specifies their renowned Heritage Putty for both a timber bead and a putty fronting finish.

For those tradespeople using oil-based alternatives, the team at Hodgson suggests using their popular Multi-Purpose Putty for a putty front fillet, while the Heritage Putty provides the bedding compound for the unit. In every scenario, Hodgson advises tradespeople to ensure all compounds are compatible with the sealant used in the construction of the IGU edge seal, and that they follow the IGU manufacturer’s recommendations.

No matter which solution is preferred, at Slenderline Glass all of the relevant glazing materials can be purchased alongside supply-only IGU orders.

It is also vitally important that tradespeople follow the recommended painting times as specified in the glazing methods, to avoid any possible flaking or degradation. Depending on the sealant used, there are different timescales for painting after glazing has been completed. Whilst extenuating circumstances such as temperature and humidity can also extend cure times, even accepted paint types can prolong drying times and must be taken into account. All of this information is available to customers on request.

Ultimately, it’s down to our joinery partners to inform their customers of the importance of following these guidelines to ensure the entire supply chain works harmoniously. It also helps to avoid any call-backs, unhappy customers and extended lead times. Many of our customers are now taking advantage of our factory glazing option which gives them peace of mind that our Slenderline units are fitted correctly, no matter which glazing method is specified.

We’ve been manufacturing sealed units of all kinds since the 1980s, with the success of our heritage operation necessitating the creation of Slenderline Glass as a standalone business in 2012. We take great pride in delivering something truly unique that combines authentic heritage aesthetics with modern-day thermal performance. With the help of our supply partners along with joiners, builders and installers, we want to make sure that continues.

For those that have any questions, or would like any further information, please feel free to get in contact.

Yours sincerely,

Andy Cocker

Director, Slenderline Glass (part of the EJ Cocker Group)

For more information call 01732 885030 or visit