David Francis is a hands-on mason who has specialised for many years on the memorial side of the stone industry. He was Technical Advisor to the National Association of Memorial Masons, writing manuals and City & Guilds Qualifications. If you have an issue regarding any aspect of memorial masonry, David is happy to help. Send your questions or comments to David at [email protected].
Lettering on Stone. How long should it last?
The answer to that is that it should last a long time. There is no definitive time scale for lettering to last as it depends on a number of factors. Lettering in soft stones in areas subject to high levels of pollution will not last as long as letters cut into a hard stone such as granite or a resilient stone such as slate. Granite is not all created equal, but Egyptian hieroglyphics cut into granite have survived millennia – witness Cleopatra’s Needle in London.
Stone used for buildings and memorials varies across the UK.
Originally, materials for both were often sourced locally. As transport has become easier over the years it has become feasible to move stone further. Initially, the most resilient stones from the country, or easily accessible nearby countries, were used. Now stone is imported from many different countries, much of what is used for memorials coming from China and India. The properties of the different stones used will determine how the stone will last in our weather conditions and how any lettering or decoration cut into it will survive.
Granites from the British Isles are chosen for memorials because of their durability and because they would take and retain a polish. But relatively softer stones such as slate, sandstone and limestone have been popular choices down the centuries because they are easier to work and shape.
Marble was one of the first types of stone to be imported for use as memorials and for sculpture. But it tends to erode when exposed, especially in salty air or acidic rain. However, provided lettering is carved into the marble materials properly, it should still be readable for many years.
To make lettering more readable, letter cutters and masons use materials to infill the cut letters. Lead, paint and gold leaf are the main finishes. Some of the modern paints and fillers are designed to be used as a single coat, although this does not always guarantee lasting results.
The porosity of the stone on which infill or paint is applied will also determine how long it will last. Stone that holds moisture can rapidly lead to the deterioration of letters, especially in freezing conditions.
Memorials, like buildings, are generally exposed to all kinds of environmental attack. UV light from the sun and acid rain dulls paint. Lead oxidises and shrinks over a period of years and tends to fall out of lettering, especially if it was shoddily installed in the first instance. Paint applied as a single coat or without a primer will also be likely to have a shorter lifespan than paints applied correctly and in accordance with the manufacturer’s instructions. Gold leaf, if not correctly applied or of lower quality, will change colour and lose its lustre.
The location of the lettering, the direction it faces, whether it is on a vertical surface or a recumbent surface and its proximity to any surrounding trees, hedges or other vegetation will affect the lifespan of the lettering. Grass cuttings stick to memorial surfaces and will also affect the length of time the lettering in-fill will last because grass left on a memorial begins to rot and can produce chemicals that affect infill materials.
Lead can be used either flush or raised. Flush lead, where the surface of the infill is level with the face of the material, is mainly used on marble. The lead is held in position by being beaten into small holes bored in the base of the carved letters. When marble erodes, the lead becomes raised above the surface and eventually falls out. Raised Lead lettering is used more commonly on Granite and hard sandstone.
The paints used to infill lettering vary from one manufacturer to another. Modern paints now have to meet stringent European regulations. In my experience, enamel oil-based paints tend to be the most durable although some acrylic paints can last for a considerable time.
As with any painting, preparation of the substrate to be painted is also a factor that determines how long the finish will last.
Lastly, a plea to all who design or cut letters: wording is meant to be read at all times, so make sure it is can be read in all weathers.