Limestone (Calcium Carbonate – CaCO3) is burnt in a kiln giving off Carbon Dioxide (CO2) gas and forming Calcium Oxide (CaO) which is commonly known as Quicklime or Lumplime. It needs to be burnt at 900-1100°C to ensure a good material is produced. The resulting lime is at its most volatile and dangerous at this stage.
The Burnt Lime or Quicklime is then combined with water (slaked) as quickly as possible. Combining Quicklime (CaO) and water (H20) produces Calcium Hydroxide (Ca(OH)2 - slaked lime and heat.* We combine it with an excess of water which produces a putty. It is also known as non-hydraulic lime because it requires exposure to air in order to carbonate and does not set under water.
Lime putty is suitable for:
i) Blending in the correct ratios with appropriate sands to produce plasters and mortars (coarse is ideal for this purpose).
ii) Diluting with water to produce limewash or lime water (fine is ideal for this purpose).
Premixed ‘wet’ products are made from lime putty with the addition of an aggregate and/or fibre to save you having to blend on site and include mortar, plaster, glaster and lime hemp plaster.
This lime is regarded as the most appropriate lime for old buildings where maximum permeability and flexibility is required especially suitable for pointing brick and soft stone work and is highly suitable for nearly all internal plastering and rendering onto cob, straw etc. See the Documentation section for application guides, coshh sheets and our winter weather warning.
Our lime putty is available in 20 litre buckets or 1 tonne bulk bags (please note if you require less than 6 tonne in bulk bags then we will probably need to ship this by pallet carriers, please note they will only accept lime putty in crates, you will therefore have to choose the 1 tonne bag in crates). For 6 tonne or above, we would try to deliver the bulk bags on our lorries to avoid the additional cost of the crates but the cost-effectiveness will depend on miles. If you add to your basket, we will save the order and get back to you with the most economic delivery.
Bulk order discounts apply to this product, the more you add the more discount you will accumulate!
- Technical Documents
- Application Advice
Fat Lime Putty or Non-Hydraulic Lime is produced by slaking fresh Quicklime (Lump Lime) in an excess of water which is then left to mature.
Fat lime putty is also known as non-hydraulic lime as it requires exposure to air to carbonate and does not set under water. This lime is often regarded as the most appropriate lime to use for applications in the conservation of old buildings where maximum permeability is required.
Fat Lime Putty can be blended with sand to produce lime plasters and mortars or it can be diluted with water to produce limewash.
Regarded as the most appropriate lime to use in the conservation of old buildings, where it is important to maximise softness, vapour-permeability and flexibility.
Keeps indefinitely - and especially well in buckets - when stored correctly.
A dedicated warehouse facility, semi-automated batching and stock rotation ensures that our putty is produced and stored to the highest standard.
We produce our own putties in Wales, at our manufacturing facility that operates under our ISO9001:2008 quality management system using British quick lime.
What is the difference between the different types of lime?
A non-hydraulic lime, or lime putty, is made by slaking burnt lime in excess of water. It can then be mixed with an aggregate to produce mortar. This type of lime is used in our premixed lime mortars which are supplied 'wet' and ready-to-use, they just need 'knocking-up' on site to release the water held in the mix. These limes are slower to set and produce a softer mortar, but their positive is good flexibility and excellent vapour-permeability.
In additional, there are 'Natural Hydraulic Limes' which are made from chalk or limestone containing clay impurities. These tend to have a faster and harder set than high calcium lime but they are less flexible and less vapour permable/breathable than non-hydraulic lime. They are available as a powder to be mixed on site with aggregates and water, or as a dry pre-mixed mortar.
Which lime should I choose?
It is important to choose the right lime for your building/application, too oftern the default is a strong hydraulic but the mortar/plaster should always be weaker than the building fabric - see Choosing a Lime in Documentation. You will need to understand the trade-offs between flexibility, vapour permeability, strength and speed of set - see table below or call 01874 611350.
How dangerous is it to use lime?
Lime is caustic, so you should therefore protect your eyes and skin by wearing goggles and gloves - see Product Safety Sheet under Documentation.
Please don't be put off though at least we know what the effects are of lime e.g. it does not off-gas toxic fumes, it does not produce toxic waste etc.
Can I use ordinary building sand to make a lime mortars and plasters?
Lime mortars and plasters generally perform best with minimal shrinkage if made with a good quality, well graded, sharp sand. This is often the difference in the price of premixed plasters and mortars therefore care should be taken that you are comparing like with like when looking at different manufacturers.
General building sand tends to be too fine. Pit sands and not marine sands should be used as they can be poorly graded. Salt residue in sea sands can cause reactions in lime mortars and we do not want to introduce salts into the building.
Do take care, we see many failures where a local sand has been chosen and it has caused various problems as listed above. We therefore introduced our own range of carefully selected and blended aggregates which have been tested over many years to give the best results, for an environmentally-friendly alternative, see our recycled glass aggregates!
Should I add a little cement to my lime mortar to give it strength?
It is often thought that by adding a little cement to lime mortars, typically in the ratio 1:2:9 (cement : lime : sand), that a lime mix can be strengthened. While this may induce a quicker initial set, this may prevent proper carbonation of the lime and produce a weaker mix in the long-term and so it is not advisable!
If you wish to increase the speed of set, perhaps consider using a pozzolan in your mix (see separate entry) or using a stronger hydraulic lime.
What is a pozzolan?
These are materials that can be added to a lime mortar to increase its set. They normally contain a form of clay particles containing silica and alumina which will combine with free lime. They are often natural materials such as fly ash, brick dust or calcined clay. They are often seen in old mortars. If you need to match an old mortar, then we are able to help, see our Mortar Matching Service.
Can I use an ordinary drum mixer to mix lime mortars/plasters?
Yes, but for larger quantities we would recommend using a forced-action, pan mixer or a mortar mill.
Where can I get hold of these mixers or mills?
We hire out and sell small 100 litre mixers and hire out mortar mills. We currently have a towable, diesel mill as well as a static for larger quantities. Care should be taken with mills not to crush aggrigate.
How do I make my own limewash?
It is usual to add water in the ratio of 1:1 with lime putty, limewash is best applied as thin as possible so you are looking for at least the consistency of single cream. You will need to apply at least three thin coats - see Application Guide under Limewash.
Should I add anything to help my limewash adhere?
The adhesion of limewash relies on suction from the surface to which it is being applied as well as a ‘finger hold’. It sticks well to lime plasters and renders, stone, brick and similar materials, but does not usually adhere so well to modern materials and finishes. However, other paints and / or additives and/or methods of application are available to help with this - see application guide under limewash.
Why do I need to protect lime work?
Lime products need to carbonate (not just dry) which they do by absorbing Carbon Dioxide in the presence of moisture. It is therefore important to create the correct conditions for carbonation, which comes through experience but is vital to the success of the set - refer to the application guides for each product for details on protection - it is one of the most important points to ensure a successful result!
Different limes, different applications, different backgrounds (even in the same building), different times of the year and different elevations on the same site will all require careful attention and possibly different measures.
Most of the failures that we see are down to a lack of appropriate tending to aid carbonation as even a poorly specified/selected lime type can actually succeed if applied and cared for appropriately after all we did not historically have the range that we have now! As a result, we concentrate on this particular aspect on our training courses and in our application guides and are happy to discuss any aspect of it with our customers - call 01874 611350! We want your job to succeed and most do!
Should I stop using lime in the winter?
It is not recommended to use lime products (lime mortars, renders and limewashes) when temperatures are liable to fall below 5°C (41°F) for several weeks/months after the product has been used, this is especially true for non hydraulic and the weaker hydraulic limes. In practice this means that unless adequate weather protection is provided they should not be used externally until next spring, however, if work must continue then please see application guides and our using lime in winter information sheet in Documentation.