Why natural linseed paint is the best option on period properties

Why natural linseed paint is the best option on period properties

By Ian Stokes of Nouveau Decor

Ever since the late nineties to the present day, driven to find high quality alternatives to synthetic paint, I have discovered and used some very good natural paints. My preference is always for traditional coatings because they combine my two passions – old buildings and paints containing natural ingredients.

I have driven many miles researching products or attending courses to build up my knowledge, but if I am going to put my faith – and my customer’s confidence – to the test then I need to be sure about what I am using.

In all those years, one product I have great confidence in and enthusiasm for is Linseed paint. My personal favourite is made by Ottosson Linseed Paint in Sweden and obtained from the sole supplier in the UK, Oricalcum. I am not averse to using other brands, and it can be argued that it is not very eco-friendly using imported materials, but I really like using Ottosson and appreciate the technical support I have received. So I compromise my green credentials for quality, order time, colour choice and overall service.

So, back to the beginning…why do I use Linseed?

Firstly, it is a pure, natural product that is environmentally friendly and completely harmless. The oil is very high quality, refined Linseed mixed with natural pigments. It is long-lasting and extremely durable, extending the time between redecorations, and is also renowned for being one of the best preservers of wood (cricket fans will already know this!). In the case of Ottosson, their Linseed is produced locally to their factory from Flax, and it is not modified in any way – by that I mean no cheaper minerals or fatty oils are added – it is pure local Linseed.

I adjust paint viscosity, flow, drying or sheen level by the addition of pure balsam turpentine or the raw, boiled or sun dried linseed oils. In the past Linseed oil was mixed with lead producing a paint with ideal properties for a lasting coating. The arrival of petrochemical paints and the hazards of using lead saw its demise in the first half of the 20th century. The revival of linseed paint needed a pigment to take the place of lead as natural ingredients are always more at risk of exposure and growth of fungus or mould. This is now attained by the addition of the safe pigment Zinc Oxide.

With a colour palette of standard colours ideally selected for their suitability for period properties and restoration projects, Linseed provides both practical and aesthetically pleasing solutions. Additional colours are available to order, hand mixed in Sweden from customer samples. Being manufactured from natural earth pigments they are colourfast with some vibrant hues in the palette. The finish is of a low sheen or matt finish appropriate to these older property types. When applied the finish appears a little grainy because of the heavy pigment content. Brushing well out for the necessary thin coat and laying off with a high quality brush disperses this well and as the finish dries with a dull sheen, it becomes less apparent. In fact, no different in some cases to its synthetic equivalents.

I am assured of the quality levels, having visited the factory in Sweden and seen everything for myself. Seeing the ingredients, the refining, and manufacturing process along with past projects and site visits to current work in progress, I left satisfied that this paint ticked all the boxes and I wanted to use it.

The range of linseed products for the painter expands further. I have had experience using linseed wax for woodwork, which I used on oak beams and looked great, and a glaze for painted decorative effects used in conjunction with their artist paints. For metalwork, priming with Iron Oxide primer provides rust protection. Having used this I found it one of the best red oxide primers available

Now let’s move away from the actual finish and focus on the benefits of preservation. I have gone back to jobs I worked on several years ago and I think the results are remarkable.

Modern synthetic paints are basically a plastic coating which traps moisture underneath the paint film until it eventually becomes less flexible. When the film finally gives way and cracks, allowing ingress of moisture, flaking begins and the damage is already done. The moisture will have already started to rot the wood beneath.

I have found countless times on previous painted jobs after being prepped, filled and repainted the process still needs repeating when repainted in a couple of years – but this next time it has rotted from where the filler finished. Where I have burnt existing paint off and the wood had moisture trapped beneath the surface it has allowed the gradual dispersion of moisture.

When painting exteriors it could be argued that modern synthetic microporous wood stains allow moisture permeability. However, each additional coat of a wood stain reduces the percentage of permeability. The more coats applied the more a thickness builds up, the more moisture is trapped inside. I have come across many jobs where the wood stain has failed resulting in splitting and flaking after losing its flexibility, and decay has moved in

The alternative to these synthetics are linseed paints. In practice I know my preferences of material. The fact that it is a natural product makes it all the better.

A comparable example to synthetic paint is one such case of a period front door stripped by the customer using a hot air stripper, it had obviously retained an amount of moisture, under the latest applications of modern synthetic paint, due to the shrinkage over the following months. However, this may have been reduced had it been stripped using an Infra-Red Speed heater. It was painted during the winter and shielded from the weather after receiving a primer and full coat. Left until spring for an improvement in weather and temperature, it dried out but had shrunk at the joints. Filled and repainted it was again left, and again it shrunk, although to a lesser extent. Again it was filled and painted and has remained stable since. There was no flaking of the paint film, it remained adhered to the timber where it had separated even though it had stretched over the joint. Having experienced similar with synthetic paint where the film stretched, twisted and flaked around the joint, I was more than satisfied with the performance of the linseed paint.

At this point I will stress that when filling it should be putty that is used for the large holes, a putty type filler for intermediate holes and indentations then Rubinol (a linseed based filler) for the finer holes, splits and cracks. I have found when using putty for filling and for re glazing windows the linseed paint goes on a treat. A big difference when applying some synthetic paints over putty when it separates with brush marks and pulls up. This makes sense as it is all part of the same system but I will say the Ottossen putty is of really good quality. 

Why is linseed so good?

The performance of linseed is enhanced because the size of the molecules in the linseed oil are smaller than water, and thus penetrate deeper into the timber, enabling water to be expelled through a wicking action, drawing moisture out like the wick in an oil lamp. During paint manufacture each pigment particle is fully coated with oil so does not hinder this penetrating action. Characteristically it joins to the material forming a bond, making it denser and dries really hard. The very small molecular size allows for excellent adhesion properties to previously painted surfaces. For me though its main advantage is the breathability, allowing moisture permeability while still remaining waterproof. 

I suppose the main disadvantage of Linseed paint is that to get the full potential of its benefits it needs to be applied directly to the substrate. Like any coating its future performance depends on the surface to which it is applied. If it is going to be applied to an existing previous coating this needs to be in sound condition. If not like any other coating it will fail. This is more important when painting exteriors due to the exposure of the elements. I have in some cases removed paint from the whole of the bottom twelve to eighteen inches of the windows if the rest is sound, as this is where the moisture sits, with success. As with all systems preparation is key to success, and for removing paint the use of the ‘Cobra’ speed heater is perfect for me. It should also be appreciated that the paint will be compromised if applied in adverse weather conditions. Therefore, the painting season for exteriors should only extend from spring until September for suitable drying conditions. This is the practice followed in Sweden and should be adopted here in our climate.

At this point it should be mentioned that when stripping existing coatings in readiness for applying linseed paint, a paint stripper of alkaline properties should be avoided as linseed paint requires a ph. neutral surface or premature breakdown will occur. 

After application, future maintenance is quicker and simpler. A wash down, light rub and recoat is sufficient or just a wipe with fresh linseed oil opposed to complete removal where the system has broken down, which is what I find so many times with the synthetic alternatives. I find it so disheartening that in the past I have practically removed 90% of paint from exterior windows and doors, given them the full treatment only to return and find it has flaked again. It is a vicious circle that the wood is obviously damp and the damp is deep into the timber and although it looks and feels dry another coat of ‘plastic’ seals any remaining damp to damage the coating with a bit more rot over the forthcoming two years.

Finally, Drying times. 

Linseed oil is a drying oil meaning it absorbs oxygen from the atmosphere during the drying process along with exposure to sunlight and a reasonably warm temperature to complete the process. The drying time of Linseed paint will vary upon the conditions in which it is applied ranging from 24 to 72 hours. I have applied this paint on exteriors on a bright summer’s day and returned the following morning to a dry coat. But I have also applied it on dull cooler days where it’s taken the full drying time. The drying process can be aided by the use of the Ultra Violet Lamp which replicates the action of the sunlight. In the interior the addition of a small amount of driers is acceptable. But the most important factor is the application of thin coats. Not through the addition of large amounts of thinners but in the way it is applied to the surface. If applied too thickly then drying will be extended along with a build-up in recesses and crinkling of the film surface.

Due to its heavy pigmentation it covers really well but may also appear grainy so requires working out well too. Application of thin coats is the key and its bulk of pigment allows for this with excellent covering properties. Adjusting the viscosity will help the flow in final finish and laying off to reduce presences of brush marks. It will not produce a high gloss finish but that is not the intention for a high gloss is a modern conception, unless a varnish was used. In my opinion this would look too polished and sharp for a period property. Natural finishes accentuate the characteristics of a tastefully restored building. If however you did require a higher sheen level this can be achieved by the addition of sun dried linseed oil.