Lime Mortar Training in Sicily

Lime Training in Sicily: Experience with Twice Burnt Hydraulic Lime Mortars

 

A lime training week was run at the end of February 2014 in Sicily by Womersley's Ltd and this is an article about the event and what was learned in the process.

 

The training area was set in an olive grove overlooking Taormina and the Ionian Sea which meant worked occasionally slowed, because at times you had to just stand there and admire the view. We tried to only use materials we could find on the site to build a kiln, burn limestone and product hotline mortars to start to repair a ruined Sicilian house.

 

The lime stone in the district of Castelmola and Taormina has been burnt in series of lime kilns built into a hillside located near to the railway station where Taormina runs down to the sea and becomes Giardini-Naxos.

 

We assumed that the local limestone would burn well to produce a quick lime. The lime reacted with weak acid and was coated with a dusty layer of calcium carbonate. With this in mind we constructed a Kiln using stone we could find on the site and clay mortar, made by just digging up the adjacent ground and mixing it with water. The clay mortar was ideal for the job and looking at local houses built before the arrival of mass concrete walls it appeared the locals also used this locally available clay mortar. In the surrounding areas there also appeared to be evidence of clay mortars stabilised with quick lime, which would be good to study further on the visit next year.

 

The Kiln was simply circular on plan tapering to a chimney at its apex. A brick arch was constructed at its base. Before the final few courses where built the kiln was loaded with twigs and small branches taken from a pile of olive branches that had been created by pruning the year before. Larger Olive wood was then cut up and loaded in, before a layer of larger limestone was laid on top. Smaller stones where then put in, before more wood and stone. The Construction of the kiln was finished and a chimney was created by standing three semi-circular roof tiles upright. To ensure the kiln was insulated and that enough of a draw was created without leakage of air the whole thing was rendered with a clay mortar, harled onto the coarse limestone blocks.

 

The Kiln was lit and we sat down to lovely local Sicilian cooking and a glass of wine.

 

The following morning we raked out the burnt limestone and added it to water. Unfortunately there was little reaction and we assumed we had not burnt the lime long enough and hot enough, we were aiming for 800-900 degrees centigrade. We reduced the height of the kiln, reloaded it and relit it. The resulting twice burnt limestone was then added to water with a reaction but again whilst it generated heat and noise the available quick lime content in the rock appeared limited.

 

However as the nearest alternative lime supply was over 60 miles away we decided using steel mesh, bought from the local hardware store, to sieve the partially burnt stone. Using the partially slaked brown quick lime that passed through the mesh we made two hot lime mixes and kept the remainder to form a putty.

 

The first hot lime mix that we used for repairing a collapsing masonry arch consisted of one part partially slaked quick lime: one and half parts sand made from crushed lava from Mount Etna and one part coarse volcanic ash that has fallen from the sky onto the ground where we were working, only a month before, when Mount Etna erupted. This volcanic ash typically

consists of 17% CaO+MgO content, 47% SiO2 concentration and 16% Al2O3. This mix, whilst lacking fatness, was used to rebuild an arch out of very poor stonework which required many pinning stones and tiles. The mortar, although hard won, set quickly and without any shrinkage. It appears that the lime we had burn contained substantial amount of silica and this had created hydraulic quicklime and when combined with ash had resulted in a fast set although it did not appear to have created a hard and impermeable or brittle mortar.

 

The second batch of mortar was made from the same partially slaked sieved quicklime, and crushed lava sand. This traditional aggregate is called azolo and is created by crushing the surface layer of the local lava flow which consists of prevalently vitreous scoriae. "Azolo", is a porous material that, after being crushed, becomes a sharp, grey to black, and forms inert lightweight sand. Research by Catania University has not detected any pozzolanic reaction between lime binders and azolo aggregate as would be usually expected when dealing with volcanic materials.

 

In to this mix of one part partially slaked hydraulic quick lime to one a half parts crushed lava sand we added one and half part of local red “ghiara”.Historically, this clay subsoil burnt by lava flowing over it, was mixed at ratios ranging from 1/4 to 1/3 to form a form a natural hydraulic mortar. Mortar of lime and red ghiara, introduced in 1860, rapidly replaced mortar of lime and azolo, thanks to its smaller lime demand, which was the most expensive material. In the post-war period, this type of mortar was replaced by concrete mortars, because of the difficulty and cost to quarry red ghiara.

 

This pozzolanic aggregate was extracted from underground quarries, crushed and then sieved. These quarries are now discarded although we managed to find an exposed seam in an old volcanic lava flow, behind a car park in the centre of Catania. We took a small quantity back to the training area and broke it up and then crushed it with a lump hammer, before adding it to the mortar. Mortars made with red ghiara (containing C–S–H and C–A–H) are present in most of the historical centre of the nearby city of Catania.

 

We then used this mix of lime, azolo and ghiara to repair, daub out and render part of a wall. Again a fast setting mortar had been created again with no evident shrinkage. This was finished with a wet dash finish of the slaked hydraulic lime, sand and azolo to replicate the old render finish on the building.

 

Finally the lime which we had left to form a putty became a solid lump after only 24 hours and had to be reawakened with a lump hammer before we mixed it with fine silica sand to create a lime plaster finish coat.

 

The whole week in Sicily included a tour of the two villages where the god farther had been filmed, a visit to Mount Etna together with a vineyard and winery on its slopes, a visit to beautiful Greek Temples, the cove of Islabella, Taormina and Castelmola. The seven days where complimented by great local Sicilain Cooking, created with local passion and pride and a little local wine.

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2018
Day 6: Promoting Tourism through Conserving Heritage Conference Final day in Ethiopia Conservation Management Plans and Goodbye Day 4 Lime Training in Ethiopia Day 5 Lime Training in Ethiopia Day 3 Training in Ethiopia Day 2 of Lime Training in Ethiopia Empress Mentewab's Kuskuam Complex Lime Training in the Royal Compound at Gonder Day 1 of Running Lime Training in Ethiopia Conservation at Guzara Palace Earth mortars and Northern Ethiopia Inspirational Wattle and Daub in Ethiopia Providing Lime Training Out of the Rain An introduction to Silicate Paints Natural Pozzolana described by Vitruvius in the Roman Era Faux Marbling and Traditional Paints Training test Spenfield House Decoration Inspires Training Day Training at the Jewellery Quarter Birmingham Lime render finish coats for innovative design Paint Stripping Samples for Wythenshaw Hall A refresher day on Hot Limes for Mono Masonry Cast Roman Cement from 1840 on a building in Liverpool The colour is great and lots of very positive comments Fiona's Sheep formed from Womersleys Stone Repair Traditional Stand Oil Paint on new garden gate Tithe Barn now finished after Womersleys supply foamed glass insulated floor Ryedale Plasterers honing their skills & techniques Stone and Brick Repairs We would love to see you at Harrogate free tickets are available here Womersleys Insulating Lime Render Plaster and Moisture Buffering New Wattle and Daub supplied by Womersleys Ordsall Chord is coming to a successful finish Oil Paints and Distempers used to create an Illusion The iron rich limestone and aggregates of south east Sicily Marbeleizing with Natural Oil Paints Lime Mortars have always had to with stand extreme weather and seas The Cathedral Church of Saint Nicolo presents a fine Baroque façade The beautiful Noto limestone cladding Noto's Baroque Buildings Beautifully weathered lime render Lime stucco repairs to capitals Brick and Stone Formwork Exposed behind Lime Stucco Render Historic Lime Kiln at Shap Lime Stucco Work by Giovanni Bagutti Plaster, Daub and Render Survey at Old Hall Farm Repairing clay daub and lime plaster on panels of riven lath and insulating externally with insulated lime renders Use of mobile elevated platforms in Theatres Creating Formwork and Constructing an Arch An introduction to Lead Work Training Day Working with volunteers on the Chesterfield Canal Helping the Canal and River Trust Volunteers Training Course Sicily Building Kiln Training Course Sicily: Chuch of San Nicola Womersleys training course Sicily It really is as beautiful as they say Traditional buidling techniques Garden Corner Tower circa 1650, Agra Living Heritage Real Market Places Fine polished lime plaster ensured opulent splendour Indian Mortar Mill India Gate Lotus Flower forming 17th Century Column Bases Seventeenth Century Chrysanthemum Detail The Lotus Flower and the Indian Flag 17th Century Lime Stucco on brick Seventeenth Century Indian Frescoed Lime Stucco RIBA accredited CPD paint seminars Ceiling Survey Reveals a Glimpse of Former Decorative Glory Clay Infill found in Exeter's Grand Royal Clarence Hotel Foamit Sub Base for Great Tythe Barn
2016
Get your free tickets for the National Home Building Show Understanding Marple Lime Kilns It would be good to see you Sensitive refurb planned for Forge Cottage Last of Five Days at Grand Designs promoting Womersleys Stabilising a boundary wall with Hydraulic Hot Lime Mortar Its nice to be appreciated Training with Help the Heroes Volunteers The historical development of a simple wall Trialling hot lime mortar Lime Mortar Training Yesterday at Womersley's Breathable and natural paints for Lighthouse Aglaia emulsions used at St Leonard's Latest build by Guy and Straw Works Ltd Advice on Breathable Insulation for a Windmill More Lime Wash for West Wycombe Park Our latest article in the Listed Heritage Magazine Toft Gate Lime Kiln in Nidderdale The whole is greater than the sum of its parts What a pleasure to be booked in to resurvey the Apollo Tim's Nidderdale Dream Womersleys helping with Conservation Skills Training Programme Lovely Chamfers Working with our German Paint Partners The Ceiling Centre Tells a Story Historic Mortar Analysis for North Bar, Beverley New Foamed Glass Sub Base for Beamish Park Gardens Refurbishment Plasterwork survey at Oakwell Hall Completed Please call in to see us if you are at the Great Yorkshire Show Renovation in the Prettiest Village in the County Offering Paint Advice at Holy Trinity Church, Hull Developing Thornton's Conservation Area Assessment to Guide Develeopment Talbot Yard Malton Wins Award Insulating an Old Building with the Internal Warmshell System The Hairy Builder (Biker) Promo Traditional and Natural Paints featured in LPOC magazine Results of Plaster Survey at Wythenshaw Hall following fire damage New pre mixed Ironstone mortars introduced Results of Plaster Analysis at Castle Dairy Kendal Womersleys continue to supply lime mortars to Pontefract Castle Plaster Survey at Wythenshaw Hall following fire damage Holy Trinity Church Sunderland Plaster Survey Investigations in to the condition of the plaster on the walls at the Exchequer Building, Palace Green Library, Durham Plaster Analysis at Castle Dairy Kendal Free Illustrated Case Studies detailing Insulated Floors for Old Buildings