Elementary lime wash question.

[michael]

When applying lime wash to external walls, there appears to be a number of ingredients that can be added to it as a binder which I presume increase its strength and durability. The three additives I’m aware of are:- Tallow fat, Linseed oil or Casein. Could one of you experts out there please explain the individual qualities and advantages that each of these additives provide? In other words why should I choose one binder over another if they're all suitable for external use.

 

[andrew gayton]

The choice without question is raw linseed oil. RLO is the easiest material to obtain, mix and apply. I would not use tallow as a matter of principle and casein in my experience is not overly effective. You only need to include 1% RLO to the total mix.

 

[Nigel Watts]

I would not use tallow as a matter of principle.

Is that because you are a vegetarian, or because of some other principle? Caesin would presumably be unsuitable for Vegan householders and their builders.

I didd't add anything to my limewash, but as it's only been up about a year its too early to say it that was a wise decision in terms of durability.

 

[andrew gayton]

yes, a vegetarian (although I do wear leather [on a motorcycle] as there is no alternative). The use of RLO is also far simpler in process terms. My flint house has had the same 3 coats on it for the last 9/10 years and is only just showing 'noses' of the flints - not bad considering the lack of porosity. If applying to a porous substrate, it should be ok to not include a binder provided it is a white limewash. In my experience, certain pigments will powder up no matter how well mixed.

 

[michael]

My local supplier of lime products (and other traditional building materials), supplies not only plain limewash but also limewash bound with either of the above three binders. These are mixed up in bulk and not just to order. It therefore begs the question, if raw linseed oil is without question the only binder one should use, then why would there be any demand for lime wash bound with tallow or casein? There is a price difference I suppose. This particular supplier sells 20ltr tubs of limewash bound with tallow at £25, bound with Linseed oil at £30, and bound with casein at £65 (2 x 10ltr tubs work out a bit more expensive than the 20ltr tub). If price is anything to go by, then this would suggest that casein is the superior product.

 

[TheForge]

That's some expensive milk! Is it large volumes that are added?

 

[andrew gayton]

From my experience, casein produces a less durable surface than RLO. You could always experiment and make up your own samples and test them - thats what I would be inclined to do if I were in any doubt.

 

[johndow]

I limewashed last year and after seeking advice from various folk, decided not to add anything. So far, and it's a bit early to be absolutely sure, the result is fantastic. I live in a particularly exposed area and put on 4 coats. I thought, up until the east winds began a few weeks ago, that our cottage felt warmer as well as drier. ( still very dry )
Another dividend of adding nothing, is the cost. For the first time, using lime became a financially cheaper option along with all the other benefits. I think that I'll be repeating every 3/4 years, going by the exterior paintwork.
Finally, wet or dry, the result looks stunning.

John

 

[worms]

My local supplier of lime products (and other traditional building materials), supplies not only plain limewash but also limewash bound with either of the above three binders. These are mixed up in bulk and not just to order... If price is anything to go by, then this would suggest that casein is the superior product.

As far as I am aware, shelf-life of casein (once mixed) is limited, so the casein version is probably made to order or suffers greater risk of spoilage, which may account for the smaller tubs and greater cost. It is also probably aimed at the indoor, decorating market rather than the bulk outdoor market.

 

[worms]

That's some expensive milk! Is it large volumes that are added?

It is also expensive for a mix of lime and water and a splash of linseed!

 

[andrew gayton]

I made 200 litres last autumn around £25 (water-lime-oil). It sits maturing until I limewash the house again this summer (or maybe next summer.....) The first application of 3 coats - following a complete repoint/grout etc of the flint walls - has lasted somewhere between 8 and 10 years. So the next coats should last the same if not longer. Saying that, it doesn't *really* need doing .................... it hasnt fallen off, just slightly worn by the weather and the noses of some of the flints are showing (as to be expected on a substrate with little or no porosity)

 

[DJH]

I just stick with four thin coats of white lime and water applied over four consecutive days with a misting of water from a garden sprayer before each coat. I only use about a 2% mix of linseed oil where the walls have been patched with cement in the past and on any large smooth stones which are usually on the corners as quoins. It's important to use thin coats for each application to prevent the lime from turning dusty.

I've one elevation on the dairy which has been rendered with a cement mortar and, as the lime wears off after a few storms I mix in some white cement with the lime... :shock:

It works for me!

Doug