1. Educational Linkage Approach In Cultural Heritage Prof. JoAnn Cassar and Roberta De Angelis – University of Malta Educational Toolkit The Conservation Process Module 4 Basic Course Exercises Topic4.C Choose the mortar mix

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3. Educational Linkage Approach In Cultural Heritage 4.3 Choose the mortar mix Exercise 4-C This detail shows the external wall of a building in Malta. As you can see, the wall has lost the mortar between the stone blocks, and it needs to be repaired to prevent water from seeping through. The wall is starting to deteriorate; the stone is soft.

4. Educational Linkage Approach In Cultural Heritage 4.3 How should it be done? Exercise 4-C Like most of the buildings in Malta, the wall is made of a soft type of limestone called Globigerina Limestone. Globigerina Limestone is a sedimentary rock formed from a loose sediment of tiny shells called “globigerinae” consolidated (compacted and hardened) into a solid rock. It is very easy to quarry and carve. Sample of freshly-quarried Globigerina Limestone Porosity: high Hardness: medium Water absorption:high Some of its properties

5. Educational Linkage Approach In Cultural Heritage 4.3 How should it be done? Exercise 4-C Look at the different mortar samples below and read their properties. Try to find the best mortar sample for re-pointing the limestone wall based on these properties. To check the answer drag the chosen sample and overlap it on the freshly-quarried stone sample. Remember (from the previous presentation) what properties are considered “good” properties when compared to the stone properties. MORTAR SAMPLE 4MORTAR SAMPLE 3 MORTAR SAMPLE 2 MORTAR SAMPLE 1 Porosity: high Hardness: soft Water absorption: high Porosity: high Hardness: soft Water absorption: high Porosity: high Hardness: medium Water absorption: high Porosity: high Hardness: medium Water absorption: high Porosity: very high Hardness: very soft Water absorption: very high Porosity: very high Hardness: very soft Water absorption: very high Porosity: low Hardness: hard Water absorption: low Porosity: low Hardness: hard Water absorption: low Freshly-quarried Globigerina Limestone Porosity: high Hardness: medium Water absorption: high Porosity: high Hardness: medium Water absorption: high

6. Educational Linkage Approach In Cultural Heritage 4.3 How should it be done? Exercise 4-C [To the web organizer: these comments should appear as pop-ups when each mortar sample is overlapped on the stone sample by the students] MIX 4 MIX 3MIX 2 MIX 1 Well done! This is a good match! The colour is not very good but it can be modified easily by a conservator. Yes, this is an acceptable match! This mortar has the same properties of the freshly- quarried stone, but it may be too strong for a deteriorated wall. Its colour can be modified. Yes, this is a fairly good match. The colour is not very good but it can be modified. It is a weak mix and will work well with the deteriorated wall. It may need to be replaced often., especially if used on external walls. Wrong match! This mortar is too strong for use with the weak masonry wall. Its colour is also difficult to modify (too dark).