Off-site grit blasting option
This is the safest, cleanest and most efficient way to prepare the surfaces. We would carefully remove the windows, panelling or metalwork and take to our facilities in Kent. There the items would be carefully hung in a blasting chamber where the items would be blasted with varying levels of grit or aggregate, depending on the material and condition. This leaves the material completely free of all paint and detritus. This is then cleaned down and air blasted ready for prep and paint. If removal offsite is not viable, you are left with a few alternative options, as listed below.
Chemical poultice
This is a great option for timber windows, as well as steel and other materials. A water-based alkaline paste is applied to windows or other surfaces in a thick layer, this is then wrapped in blankets and left for 24-48 hours, depending on what the sample area has shown. The blankets are then peeled off and, normally, most of the paste remains stuck to the blankets. The paint, and lead content, is retained within the‘ poultice’ which converts any lead present into a compound that can be safely disposed of without endangering the environment. We then remove any excess poultice and wash the windows down with water. Once the window is clean and dry, the whole surface would need to be neutralised with a slight pH acid based cleaner before any painting can be undertaken. This is a lengthier and more detailed process but has benefits as glass and reveals can remain undamaged. This type of paint removal does not allow access to the hidden faces or the window or the U-section around a steel window though, which is often unpainted and a source of rust or rot, so windows in very poor condition may require full removal.
Handheld chipping or scraping method
This is another on-site option, but it is time-consuming and carries a risk of damaging the windows and glass. Unlike chemical poultice or grit blasting, this method offers less controlled removal. In this scenario, working areas must be closed off, debris cleaned regularly, and PPE / RPE requirements are higher. It is generally better suited for cleaning one face of the window – such as external T-bar faces or internal closing edges – or where the windows are galvanised.
On-site grit blasting method
There is one other option which is on-site grit blasting. This has a significant impact on the health and safety requirements of the whole site. Normally any grit blasting requires a large generator which can be noisy, costly and creates fumes, and requires venting and locating outside. All operatives are required to wear full body RPE and significant hearing protection as the work is extremely noisy. This level of set up and facilities is not possible on all projects but for some it is very well suited.
For more information on ASWS, please visit asws. co. uk.
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