The industrial chemically manufactured paints and coatings undoubtedly have seen enormous technical developments during the last century. The question that is asked more and more often is: Why are paints manufactured in ever-increasing volumes which renounce the use of modern ingredients from synthetic chemistry and why are they sold successfully?
At first, one could be made to believe that these products are just following a fashionable trend which consists purely in putting the natural and unspoiled issue at the forefront. Such thinking would not at all give justice to the basic idea and intention of natural finishes. It is much more, above all trendiness that convinces manufacturers and users to use natural coatings to impregnate and protect surfaces.
The basic rules for natural paint manufacturers are:
• Abandonment of crude oil-based raw materials
• Unobjectionable raw materials and their compositions for all living creatures
• Problem-free integration of raw materials and their compositions into the natural cycle
• Raw materials from sustainable resources are preferred to synthetics
• The production and the growing and winning of raw materials, as well as the complete coating, must follow ecologically sound principles
• All used raw materials must be declared in simple form on the product label
This article aims to explain a couple of reasons which are of importance to the manufacturing of natural
coatings. For this purpose, it makes sense to divide paints into its basic raw material groups.
3. Pigments and colouring components
The binders are an indispensable component of all paints and coatings. In clear, non-coloured, systems does it form the impregnation or coating itself and in coloured systems, it serves additionally as a carrier of the pigments.
Properties of synthetic Binders
Synthetically produced binders have over the past decades conquered all sectors of coatings. The main arguments for that are:
• Low cost due to low raw material cost (crude oil)
• Vastly improved resistance to mechanical, chemical and other influences (easy cleaning, mar resistance, etc)
• In general, strongly reduced drying time resulting generally in ease of application
Facing these benefits, the question may be allowed: Is the use of natural binders – generally of plant
origin- not really a step backwards in terms of what has been achieved technologically?
If analysed closer one will find that natural binders are not used for ideological reasons but rather for
their advantages from a paint technology point of view.
Synthetically manufactured polymers generally consist of giant molecules. The synthetic coating is
normally a solution of such polymers in a solvent.
During the application of such coatings, the solvent evaporates, and the synthetic polymer remains readily on the surface. This explains the extremely short drying time but also one of the major disadvantages of such systems: The giant molecules are microscopically small but are still much larger than the average diameter of the fine pores and capillaries for example of wood. For this reason, the synthetic polymer is condemned to just lie on the surface. It hardly has a chance to penetrate into the substrate and to bind and anchor with the microporous system of the substrate.
It is easy to imagine that such binders have a fast drying but due to the scarce connection to the substrate also come of it easily which shows as cracking and peeling etc.
This is completely different within natural coating materials used plant oils. They dry extremely slowly due to their tiny molecule size in their application state. These minute molecules are able to penetrate easily into the substrate’s micropores. Only once they have penetrated starts what has been done to synthetic polymers during their chemical manufacturing process: the cross-linking of the tiny particles to larger, resin-like structures. Superficially this cross-linking is recognized as drying which takes longer than just evaporation of the solvent. But this way the cross-linked structure is bonded to the substrate in such a way which is unthinkable with synthetic polymers.
Concerning the drying process, the following needs to be said: A forced drying is not the paint technology ideal. An oxidative drying process (cross-linking smaller molecules with the help of oxygen to larger molecules) like one of the natural oils is never really finished. A forced oxidative dried system will also become brittle quickly were as relatively slow drying system remains elastic and flexible for a much longer period.
Other Synthetic Polymer Problems
One of the basic rules in chemistry: No chemical reaction is complete! This holds also true for the manufacture of synthetic polymers since a small amount of the starting material, the so-called monomers, remains un-reacted. They are part of the synthetic polymer and remain in the polymer as an impurity and will in polystyrene be mono styrene or in urea-formaldehyde binders be formaldehyde.
Properly polymerised components are generally physiologically harmless since they have little or no tendency to evaporate due to their giant molecule structure. The so-called monomers evaporate readily and migrate from the paint film and reach the air we breathe. Concentrations are reasonably low.
Nevertheless, should this factor not go unrecognised since a lot of monomers due to their chemical nature most likely are of high risk when absorbed for many years. Formaldehyde, for example, is a known carcinogen or cancer-causing material but lacquers given of large amounts of formaldehyde are still the preferred coating material in the South African woodworking industry.
To avoid high concentrations of monomers the chemical industry aims to provide polymers or binders that are as completely reacted or polymerised as possible. This, however, causes another problem. Due
to the high uniformity of fully reacted polymers, these tend to be rather brittle. Where natural polymers or binders mostly are already very flexible suitable paints cannot be manufactured from such fully reacted synthetic polymers and one needs to artificially create flexibility by adding plasticizers. These are purposely brought into the polymer film as impurities. Unfortunately, migrate plasticisers from the paint film and given off to the environment and risk from yearlong exposure cannot be ruled out.
In this context, nature proves again to provide the right solution. Natural binders are chemically very impure and contain many impurities. These impurities at first might seem useless and disagreeable but are in fact natural plasticizers. Natural binders generally do not need the addition of artificial plasticizers.
Further Synthetic Polymer Problems
The described giant molecule structure leads to further problems. The resulting coating films which are not properly anchored are very thick films and present a massive barrier for all gases. An exchange
between the substrate and the air is not possible: the film seal completely which results in a number of problems i.e. flaking, moisture entrapment, degrading of plaster, and many more.
Another problem of synthetic binders is their extremely high “embodied energy” values. The embodied energy value determines how much energy was used to produce such a component Embodied energy is the energy consumed by all of the processes associated with the production of a substance from the acquisition of natural resources to product delivery, including mining, manufacturing of materials and equipment, transport and administrative functions.
And more problems:
They are derived from petrochemicals, create a high level of hazardous waste during manufacture, and are toxic during manufacture and toxic during application. Waste paint needs to be treated as chemical waste.
In summary, the following can be said: Natural binders when compared with synthetic polymers initially seem to show certain disadvantages. If analysed in more detail these disadvantages appear to paint technological benefits which are even combined with bio-ecological advantages. Even here it shows that using natural binders is by far not a backward step. Prove that this assumption holds true is the fact that various synthetic paint producers include natural resins and binders to their recipes to benefit from these positive technical properties. Natural paint manufacturers in this regard go a lot further and consequently use natural ingredients only.
Especially the solvents in synthetic coatings have been subject to discussion of late. The numbers are indeed impressive if one considers how many thousands of tons of solvents are brought into the atmosphere by paints and coatings alone, in 1996 = 59.400 t for South Africa.
On the other hand, are solvents partially indispensable for coatings as the other three ingredient groups (see above) are normally applied in liquid form (spray, brushing, dipping, etc). Then again it is the] solvents which easily defy human control. Once they left the coating, they practically unguarded influence the paint user, their environment and the whole atmosphere (evaporation to a gaseous form). Based on this principle uncontrollability of the gaseous components in a coating, a high concern in the selection of such solvents should be given. From a biological and ecological viewpoint, it needs to be said that nearly all solvents in synthetic coatings and paints are to be considered very problematic.
The often-used mineral turpentine contains impressive amounts of so-called aromatic hydrocarbons. Their root component Benzene and some of its derivatives are well-known carcinogens.
The named solvent group and other solvent varieties have in common that they are mostly compounds which in such forms and concentration are not found in the natural environment of humans. The human organism is such faced with active substances which do not fit into the spectrum of the known components. The reaction of the organism to such unknown substances is normally an activation of the immune system which can have detrimental consequences.
The human organism as well as other parts of the ecosystem, however, will be familiar with solvents of natural origin. Gaseous substances like these natural solvents are in the environment for millenniums
since they always were part of the eco-system. During evolution, the human organism through numerous mutual processes had a chance to adapt to essential oils so that no unforeseen risks are taken. Even if it can come to problems with natural solvents for example “Gum Turpentine” (skin allergies) does this not contradict the above argument. Such phenomena normally only occur during massed contact with such solvents i.e. cleaning of hands. Such concentrations even of natural materials are always a crucial factor due to the radical degreasing of the skin. In this particular case, it will only be necessary to change the practised working habits since the dermatological risks are known. The occasionally occurring allergies even against small amounts of natural solvents are on the other hand due to high sensitisation of modern human beings which indeed is caused by the ever-increasing pollution of our environment.
In summary on the subject of solvents can be said: Solvents of vegetable origin belonged at all times to the natural environment of humans. They are familiar to the human organism since millenniums and thus should enjoy preference over all synthetic solvents.
Due to the high concentration in which they can be found in natural paints contact with skin and mucous membranes should be avoided even with natural solvents.
Of late even conventional paint manufactures propagate so called “solvent-free” systems. From a biological paint point of view, one can note that in these “solvent-free” mostly water-based systems basically nothing has changed in the other paint ingredients.
Merely the solvent component is replaced by water and a powerful emulsifier. And to make the whole thing functional up to 15% solvents like Butyl glycol, Propylene glycol and white spirits are added back to the recipe.
Especially in the field of the binders remain the high molecular, synthetic substances the main principle of such products. Hence can these “solvent-free” systems not be called eco-friendly as they are not combinations of natural ingredients from a biological point of view.
Pigments are materials which give paints colour and other optical properties. They are either used in low concentrations that the coating remains translucent i.e. glaze or in high concentrations to completely hide the substrate i.e. solid colours or wall paint.
Natural paints normally contain pigments of natural origin, the so-called “earth pigments”. These have the advantage that they are available in abundance. Their colours are exceptionally harmonic,
conservative and unobtrusive. In addition, show these “earth pigments” high light and weather fastness and compatibility with all binders. Most of the “earth pigments” are also free of poisonous impurities i.e. heavy metals. Here also the main advantage is that “earth pigments” are familiar to humans for
millenniums. They belong to oldest colouring agents available to humankind i.e. bushman drawings or body painting for ritual purposes.
Synthetic pigments, in general, are manufactured by rather toxic and very energy-consuming processes. In addition, a lot of these pigments contain large amounts of heavy metals like lead. Whilst European countries have since long forbidden the use of certain chemicals and raw materials in paints they remain in use in South Africa. Only very recently we were reminded how careless the industry plays with our children’s health providing toys laced with lead pigments. The dangers of lead are well known for a long
time and yet the low cost is given priority rather than common sense which should dictate the highest regard for health, environment and children especially prone and sensitive to the chemical onslaught.
Location: Home – Sunday’s Paper Lead paint alert 23 October 2005
According to the US Consumer Product Safety Commission, “lead-based paint is a major source of lead poisoning for children”. Symptoms of long-term exposure to lead described by both the commission and
South Africa’s Medical Research Council can include:
*At early stages: “persistent tiredness, irritability, loss of appetite, stomach discomfort, reduced attention span, insomnia, and constipation”;
*At severe levels: “retardation of mental and physical development”, anaemia, damage to the kidneys, and a delay in the onset of puberty; and
*At very severe levels: “irreversible brain damage”; and, eventually, death.
According to the US Consumer Product Safety Commission, “lead-based paint is a major source of lead poisoning for children”, which occurs when children eat lead paint chips or soil containing lead dust or even inhale lead dust from paint over long periods. And, while adults can absorb only 10% of lead into their bodies, young children can absorb up to 50% of ingested lead, according to the California Poison Control System.
With long term exposure to lead, symptoms described by both the Commission and South Africa’s Medical Research Council can include:
*at early stages: “persistent tiredness, irritability, loss of appetite, stomach discomfort, reduced attention span, insomnia, and constipation”;
*at severe levels: “It can retard mental and physical development”, cause blood anaemia, damage the kidney, and lead to a delay in the onset of puberty;
*At very severe levels: “It can cause irreversible brain damage”; and, eventually, death;
*Although a child’s health is affected negatively by blood lead levels between 3 and 10 micrograms per decilitre of blood, a child with a blood lead level of 10 micrograms or more should be considered to have lead poisoning
As no other ingredient group, it is especially the additives that are subject to lots of public discussions. At the forefront are the fungicides, bactericides and insecticides. All these substances are almost always materials which are not found in nature, especially chlorinated hydrocarbons. To guarantee full effectiveness it is necessary to add relatively high concentrations (1-5%). Especially fallen into disrepute are Pentachlorophenol (PCP) and Lindan. These materials also belong to the group of poly-chlorinated hydrocarbons. Even though synthetic paint manufacturers, on the one hand, maintains not to use these materials any longer but on the other hand also don’t elaborate on the substitute products they added to guarantee effectiveness against fungi and insects. The replacements should be treated with scepticism since they partially also belong to the group of polychlorinated hydrocarbons.
Basic concerns should be upheld for all synthetic chemicals which with time evaporate from the paint film which is mostly the case. The air in our rooms is permanently enriched with these chemicals and the long term effects cannot be predicted. It is the “green” thinking opinion that these chemicals should only be used rather hesitantly or not at all. It has been found that fungicidal treatment as propagated in the past for certain areas to be completely senseless. Wood pests of either fungal or animal need a certain degree of wood moisture which is not found with modern building techniques with the exception of roof structures, doors and windows. In all other areas is the protection of wood not only needless but risky and damaging.
In summary, it can be said that natural paints and other decorative finishes made from natural raw materials are a direct replacement for today’s conventional paints manufactured from petrochemicals.
They do not intend to make huge short-lived turnovers but to aim for quality and to improve the lives of all that have abstained from toxic synthetic paints and have beautified their home and surroundings by using safe, non-toxic natural paints.