Stone & Brick Cleaning – How we do it

The Doff  (or Thermatech) Cleaning System

The DOFF “Superheated water” system is very different in action to other ‘steam’ or ‘hot water’ systems currently available on the market and should not be confused with them. It uses ‘superheated’ water which exits the nozzle, in a fan pattern. The system uses a normal water supply, which then enters a high pressure pump unit, here the pressure is increased to the required level before entering the ‘Hotbox’. The pressure can be adjusted by the operator and is independent of temperature settings. Within the heater unit, the temperature can be increased up to 150°C, before it passes through a heat resistant nozzle. This nozzle directs the super-heated water onto the surface to be cleaned in a scraper like fan. It is then a case of moving ‘the scraper’ over whatever is being cleaned in an even and methodical manner.

This system can be used to remove organic matter (mosses / lichens / algaes) from most surface especially stonework and brickwork. The heat of the water also helps to kill the spores of organic matter thus increasing the length of time needed between cleaning. This does not however stop all regrowth. To do this then a biocide of some type will be required. Advice can be given on this after contacting us with your requirements. This system is also used to remove paints from stonework and brickwork – in some cases a paint softener will also need to be applied to the surface to assist in removal.This system is very kind to the substrate that is being cleaned and is therefore liked by listed building officers throughout the country.To see the difference between a normal pressure washer and the DoFF System please look at the photo below. The stone being cleaned was a portland stone usued on a wall as a coping stone. The area on the right was cleaned with the Superheated water wheras the are on the left was cleaned using a high pressure pressure washer. The area in the middle was the control area – i.e. left dirty !

DoFF vs Pressure Washer

Abrasive Cleaning / Blast Cleaning (with or without water)

Blast Cleaning is also called shot blasting, grit blasting or sand blasting and can be used in cleaning various materials including wood, stone, brick and metals by propelling an abrasive substance at the surface using compressed air. The abrasive you use varies depending on what is being cleaned and what is happening to it after it has been cleaned – for example you don’t want to use a hard material when cleaning soft stone. To my mind this is an art not a science ! There are so many variables that need to be taken into account that it is difficult to put it into one or two paragraghs.

Care must be taken to cause as little damage as possible to the substrate being cleaned and therefore you should ensure that :-

a) the correct strength / type of abrasive is being used

b) the correct air flow and pressure are being used

c) do you need to use a dust suppression sytem to contain the dust created?

The uses of abrasive blasting are vast and if undertaken by an experienced operator you should be fine . One word of caution though –

You can’t make a silk purse out of a sows ear !

Before you remove any coating / paint etc from anything ask yourself why it was put on in the first place? What is it covering up?

As well as the stone cleaning other tasks that abrasive cleaning can be used for :

Removing Limewash from Random Rubble Stone walls / Remove paint from engineering bricks / Working at low Pressure remove sulphation from Bath Stone Door/Window  surrounds / Graffiti Removal / Clean up old Beams Distress New Woodwork to make look older / Remove Paint and Rust from truck body and mobile plant (machinery) / Remove Rust and old paint from antique cast iron railings / Remove dirt and loose mortar from random rubble walls / Clean Saw Marks from and distress New Oak Beams / Clean up and remove paint / stain from staircases and wooden banisters / Remove paint from wooden tongue and groove / Clean old tractors back to bare metal prior to renovating / Strip off paint from narrowboat to leave a key for new painting/  Clean up Steel in old steel frame buildings / Remove years of grime from wooden stable stalls

Applying a Poultice

Poultices can either be made up or bought in – they are used to apply a chemical onto a surface for a length of time to help in either ‘drawing out’ substances from stonework (e.g. to remove the green copper staining) or to soften up a substance that is sitting on top of the substrate (e.g. to remove sulphation from under window cills or weather protected walls). Using a poultice will depend upon what is being cleaned anad where it is.

For further information please either call us on +44 (1666) 841338 or email us via the contact us page.