CULTURAL & HISTORICAL BUILDINGS


NATIONAL TREASURES Richard Osborne, Managing Director of stone care specialist LTP, discusses


the maintenance considerations to be made when caring for stone surfaces in historical locations.


From the grandest palace to the tiniest chapel, historic buildings are national treasures that need to be carefully preserved. Stone surfaces are a huge consideration but the methods used to protect them are changing. More and more organisations, like the National Trust and Historic England, now have sustainable maintenance policies in place relating to a zero carbon footprint, and this is helping to fuel the switch from spirit-based sealers to water-based treatments.


Sealers: The Big Debate


The debate on whether a water-based sealer can provide the same performance as a spirit-based product has been a hot topic in our industry for some years. Spirit-based sealers - sometimes referred to as oil-based sealers – use spirit (often white spirit) as their ‘solvent’, i.e. their liquid base into which other components are dissolved. Water-based sealers use water as their ‘solvent’. Spirit-based products are flammable and create the strong odour that’s evident when a surface has been freshly sealed. As Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) legislation gradually filters through, more and more raw materials used in spirit-based formulations are being withdrawn as they are now considered potentially hazardous for both human health and for the environment. As a result, concerted efforts are being made to replace recently banned raw materials from sealing solutions, without negatively impacting on performance.


Spirit is added to a sealer to facilitate application, drying and the formation of an even seal below the surface of the tile or stone. During application and drying, it evaporates and the fully-cured sealed surface no longer contains spirit. However, when it evaporates, it releases Volatile Organic Compounds (VOCs) into the atmosphere, which has a negative, toxic impact on the environment. The spirit odour can also taint materials, like curtains and upholstery, which is a further consideration in historic settings.


A New Breed


Advances in technology have resulted in a new breed of water-based impregnating sealers (also referred to as acrylic sealers) being offered as an alternative to spirit-based products. From a performance standpoint, technological advances mean that high quality water-based impregnating sealers are, in many respects, equal to or superior to their spirit-based equivalents, offering excellent durability,


— 20 —


quick drying times and the emission of less odour. But not all water-based sealers are spirit-free. Many contain ‘co- solvents’ - spirits present in lower concentrations that are meant to help push the rest of the water out of the coating as it dries. But since water-based solutions are either spirit- free, or contain less spirit, both provide a safer alternative to a traditional sealer.


Once applied and cured, water and spirit-based sealers function in a similar fashion. They are both tough and durable. Both types also provide water and stain protection and are easy to apply. But one key difference between them is their appearance: spirit-based sealers tend to be clear as the sealer polymer and the spirit-base form a continuous clear solution, whereas water-based sealers mostly appear milky white until they have cured. This is because the polymers are present as separate particles and scatter visible light differently than the water in which they are dispersed.


As well as providing a far safer option, water-based treatments also provide other benefits. Because they are fully transparent to UV light, they don’t undergo the photochemical breakdown experienced by some more UV-absorbent spirit- based sealers. They are also safer to transport, handle and store. As a general rule, water-based sealers also tend to go further than spirits, with a typical extra coverage of between 10-20% on most surfaces.


As a final point, it’s also worth mentioning that sealing, as opposed to not sealing at all, provides its own environmental advantages. The main one being that a sealed surface requires much less cleaning. This, in turn, reduces associated waste and water consumption - and eliminates the need for more drastic, costly and time-consuming intervention with harsh chemicals!


www.ltp-online.co.uk www.tomorrowstileandstone.co.uk


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32