Masons Mortar Ltd
77 Salamander Street
Edinburgh EH6 7JZ

Tel: 0131 555 0503
Fax: 0131 553 7158

Masons Mortar Ltd
Unit I, Woodville Court
Woodville Street
Glasgow G51 2RL

Tel: 0141 445 4812
Fax: 0141 445 8898

Masons Mortar Ltd
Block 2
Woodend Industrial Estate
Cowdenbeath, Fife

Tel: 01383 514 460

Masons Mortar Ltd
Unit 11
Brough Park Trading Estate
Fossway, Newcastle upon Tyne

Tel: 0191 908 9234

Lime Putty : site mixed mortars.

Designation CL90 - CL80 or CL70 in accordance with BS459 lime putty is traditionally a non-hydraulic paste or powder derived from slaking Calcium or Magnesium Oxide with water forming an Hydroxide.  The Hydroxide of Calcium or Magnesium can be stored in a wet plastic paste or as a dry powder, both are chemically identical, irrespective of the method of slaking. Both processes generate considerable heat. Left to slake uncontrolled the temperatures can be high enough to create combustion in timber.

The amount of water used when slaking will determine whether the Hydroxide is formed to a dry powder - minimum water content or a paste Lime Putty.  Mixing the powdered hydrated version of Calcium or Magnesium Hydroxide with water to form a paste is also used to form Lime Putty, historically this was termed "Souring the Lime"

As supplied all Masons Mortar Ltd High Calcium Lime Putty is fine sieved, matured for not less than 60 days and has a wet plastic density of 1.35KGs per litre minimum

Combining or mixing lime putty and sand on site manually requires considerable effort, kneading, chopping and beating the lime putty and sand together vigorously until an even uniform colour is achieved.

Mechanical mixing produces the best results.

Roll Pan Mixers - consisting of a pair of rollers that are set at or just above the height of the largest sand grains - called laying a bed, prevent crushing of materials below a certain size.  Roll Pan Mixers produce the highest possible quality mortars with the lowest water content.  On average the mortars made in a Roll Pan mixer will be 20 - 30% stronger than other types of mixers where higher water demands to achieve a cohesive mix are required.

Force Action Mixers - blades that revolve within a drum, occasionally the blades are static and the drum revolves.  These types of mixers can very rapidly cut through, fold, turn and combine stiff materials very efficiently - set to the correct rotational speed they plow through the materials rather than push the mix around the mixer pan.
Lower priced units have slower rotation, suitable for plasters and the like, but not for dense thick semi dry material used to form the best quality Lime Putty based mortars.

All lime putty mortar made with wet sand benefit from being stored for as long as possible before use.
Best quality mature lime putty tenaciously holds onto water, wet sand has a fine water film on the surface of the grains and this makes the putty/sand interface weak, maturing together for a month or so the lime and sand will form intimate contact and improve the quality of the mortar.

Once mixed and stored to mature, free fall mixers and paddle drill mixers are excellent for re-working matured lime putty mixes and adding water for plastering, rendering and the like.
For heavy dense impervious masonry build, keep the mortar as stiff as is practical - it is always best to use a Roll Pan or Force Action mixer in these situations.  Plaster, render, bedding mortars for laying bricks and mid to high suction natural stone masonry all require wetter mixes, drill paddle mixers and free fall mixes suit the purpose adequately.

Lime Putty Mortars for Gauging.
Similar mixing practice is required for lime putty mortars that require a proportion of hydraulic lime to make them complete mortars.  One significant difference is the method of combining the gauging material, in this case hydraulic lime.  The proportions of hydraulic lime will be determined by the specifier, however the following procedure should be followed.  The hydraulic lime should always be mixed with clean water to make a very stiff paste before mixing as previously described with the lime putty mortar.
Typically supplied, as a 1 : 6 coarse stuff,  the mortar would normally be gauged with 1 part NHL 5 to 6 parts of the pre-mixed mortar, thus making a 1 : 1 : 6. (1 : 3)
Whereas supplied as a 1 : 5 coarse stuff would normally be gauged with 1 part NHL 5 to 5 parts of the pre-mixed mortar, thus making a 1 : 1 : 5 (2 : 5)
Once mixed, gauged mortars can be reworked for many hours.(up to 48 hours depending on the gauging material used)

In all instances the Gauging component should be specified by weight.  Very fine powders such as hydraulic limes are difficult to measure accurately by volume.  Your Masons Mortar Ltd sales or technical department can advise you on the correct weight of each of the binders we stock and what proportion, by weight, they should be used for any given mix.
Gauged mixes can be mixed in most forms of mixers, but if the materials are to be used for bedding dense impervious masonry, keep all the mixes as stiff as practical and use Roll Pan Mixers or Force Action mixers where possible.  Alternatively use drill paddles and free fall mixers, set the mortar aside, and allow to fatten up before use.

Quicklime Mortars: where the quicklime and sand are slaked together but not used immediately, can be made with an excess of water to a wet plastic condition, covered and stored for not less than 48 Hours, and comprehensively remixed, covered and stored for a further 24 hours before use.  Alternatively slaked to a dry hydrated lime sand mortar, it can be stored under cover - loose covers are suitable, until it has fallen to a fine dry powder.

Hot Lime Mortars - The terminology for the use of mortars made by Slaking Quicklime and Sand together with water and using them immediately. The reaction of quicklime and water produces an Exothermic Reaction that initiates a chemical change in the Quick Lime (Lime which has been processed in a kiln), but has not been chemically transformed from its Calcined state to "Hydrated Lime" in accordance with EN BS 459

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