Researchers at Cardiff University, Wales, have devel­oped a novel coat­ing designed to pro­tect ancient lime­stone build­ings from olive oil derived fatty acids.

The new prepa­ra­tion, which com­bines oleic acid with flu­o­ri­nated sub­stances, was devel­oped in answer to the ongo­ing dete­ri­o­ra­tion of build­ings such as York Minster, one of the UK’s largest cathe­drals.

Buildings such as York Minster have been around since 600AD and have suf­fered from a huge vari­ety of pol­lu­tants, includ­ing sul­phur diox­ide and acid rain, lead­ing to mas­sive dete­ri­o­ra­tion of the stone. This dam­age is not just a result of mod­ern day pol­lu­tion, it dates back to increased air pol­lu­tants in the indus­trial rev­o­lu­tion.

Attempts to restore York Minster and other sim­i­lar build­ings to their for­mer glory have in some cases been detri­men­tal and in fact sped up the dete­ri­o­ra­tion. However, the appli­ca­tion of the new coat­ing to stones from this par­tic­u­lar cathe­dral have had good effect.

The new olive oil derived sub­stance could be used to coat build­ings such as York Minster and other lime­stone con­struc­tions and act to pro­tect the struc­ture from pol­lu­tants, while still allow­ing the stone to “breathe.” This dis­cour­ages the build up of molds or salt on the sur­face, fur­ther adding to the pro­tec­tion as an excess of salt can lead to crack­ing of the stone over time. This behav­ior dis­tin­guishes the new coat­ing from those used pre­vi­ously in restora­tion, which often blocked the micro-struc­tures of the stone and ended up pro­mot­ing mold and salt accu­mu­la­tion.

Limestone reacts chem­i­cally with sul­phur diox­ide and sul­phate par­ti­cles in the air, which leads to dete­ri­o­ra­tion, but one coat­ing of the new sub­stance has been found to min­i­mize this. When devel­op­ing the coat­ing, it was nec­es­sary for the team to use a hydropho­bic or water repel­lent sub­stance, in order to repel acid rain. Oleic acid is thought to be ideal for this as it con­tains a long hydropho­bic struc­ture that will repel water with the other end of the mol­e­cule react­ing with the lime­stone selec­tively.

There was also the ques­tion of the affect on the appear­ance and color of the build­ing to con­sider. Researchers had pre­vi­ously exper­i­mented with lin­seed oil on the stone of York Minster, but this was deemed unsuit­able as it dis­col­ored the stone and made it darker.

After the suc­cess of the coat­ing on York Minster, researchers have sug­gested that there is the pos­si­bil­ity to pro­tect many other ancient lime­stone build­ings in the same way.



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