The effect lead has on paint
I recently bought gloss enamel paint from a well known paint manufacturer. The surface was well
prepared and coated with a white universal undercoat, also from a well known paint supplier, and left
to dry properly. When I applied the top coat (sunflower yellow), it appeared as if the paint did not stick to
the surface well and that several strokes of the brush were required to get some sort of coverage.
The painted surface appeared to be oily and transparent with very poor coverage with the first coat. My first
thought was that the brush was to blame, but even a new brush produced the same results. When the
second coat was applied, it was clear that even more coats would be required to bring out the real colour
of the paint. To aggravate the situation, I realised that due to the thin film of paint, even the smallest
irregularity on the surface was also magnified.
During a discussion with the technical department of the enamel paint manufacturer, I was told that the cause of the problem is the removal of lead from the paint. According to them, all paint manufacturers experience the same problem. My question is, are we left with inferior quality paint due to the removal of lead and what can be done to solve this problem?
Eben Smit, by email
Technical service consultant at Prominent Paints, Pieter Greef, replies: Removing lead from paint has caused pitfalls that can and will be overcome. Firstly, lead was used in paint as a colourant, with chrome oxide (lead chromate) and red lead (lead oxide) the two main lead-containing colours. Secondly, white lead (lead carbonate) was used in paint to impart density and opacity.
The brighter the colour, the less opacity it will have and coverage is compromised. Lead chromate in a yellow colour would have assisted in enhancing the opacity of the final product. Due to the use of less titanium dioxide or lead carbonate (in the old days) in the translucent base used to tint the specific colour, manufacturers must instead make use of colourants to enhance opacity of the product.
Lead-free colourants are more expensive to manufacture as inorganic and organic colourants, pigments and surfactants are used. Different grades of colourant are available and uninformed use of inferior ingredients will affect the coverage of the product. The cost of brightly coloured paints has increased substantially due to the steps required to create a close equivalent colourant. Most manufacturers choose to reformulate their colours to improve coverage. It is the onus of the paint manufacturer to equal the opacity as close as possible to the old lead chromate.
To date there has not been a true, direct replacement for lead oxide or lead chromate in South Africa. Pigment manufacturers are continuously working on closing the gap between lead-free colourants and lead oxide or lead chromate. Continuous improvement is being noted.
For more information:
Enamel or acrylic paint?
This topic has bothered me for many years and I have never managed to find a helpful answer. If I’m coating a previously painted surface, how do I know what type of paint was used. I assume it is important to know because water-based and oil-based paints are very different.
1. Is it possible to ‘prime’ an existing oil-based paint with universal undercoat and apply water-based paint over this? I prefer to use water-based paints because cleaning the brushes and rollers after use is so much easier.
2. Is there an advantage to using enamel over water-based paints?
Tony Hale, by email
A Toni Stella the Paint Fella replies:
Determining whether the surface was painted with a acrylic or oil-based paint is very important.
Testing for an oil base:
• Soak a cotton wool ball or very soft cloth in methylated spirits, alcohol or lacquer thinners and rub it back and forth over the area.
• If the paint rubs off (dissolves) and you see the other colour below, you know it’s a acrylic product.
• If no paint is removed, it’s an oil-based paint.
Oil-based enamels can sometimes be painted directly over acrylic (however, it is not acceptable industry practice). Special preparation is needed to cover oil-based paint with acrylic.
Covering oil-based enamels with acrylic:
• Surfaces previously painted with oil-based enamels must be abraded with a Scotch-Brite pad and a solution of sugar and soap.
• Rinse with clean running water and repeat until a matt surface is achieved.
• Apply a coat of Plascon Multi-Surface Primer and allow it to dry for four hours at 23˚C.
• Apply the final coat of acrylic paint.
• Your brushes and tools can be cleaned with water.
When to use a spray gun
When should I use a normal paintbrush for painting, and when should I consider using a spray gun? Why is it better to paint a palisade fence with a brush than with a spray gun?
Brett van Rooyen, Centurion
Bruwer Leykauf, our technical consultant, replies:
When using a spray gun there is a thing called ‘overspray’, so when painting thin materials like palisade fencing, the amount of paint that you lose is great. But, on the other hand, the finish will be of higher quality; a lot smoother and with no brush marks.
When using a paintbrush on palisade fencing the coat is a lot thicker than when using a spray gun. My advice is that if going for the spray gun option, choose a spray gun with an adjustable spray pattern. Also, use a cardboard box behind the fence that you are spraying as this will act as a deflector and will allow some of the overspray to coat the other side of the fence. The cardboard needs to be placed about 5cm behind the fence.
Should you need any further information contact Bruwer on 083-234-7123.
I stay in an estate with 21 homes that all have the same problem with their driveways. The paving is 10cm-thick solid concrete finished with a hexagon pattern. Everyone painted their paving with different types of paint, but all have the same problems, including discolouration, flaking, tyre marks and deterioration of the concrete if not painted regularly.
Hendrie Spies, by email
Technical service consultant at Prominent Paints, Herman Rabe replies:
As always, surface preparation is at the heart of any successful DIY paint job. Start with an acid wash solution of ‘spirits of salts’ (diluted 1:10 parts of water). After that, neutralise the surface with ProGold General Purpose Cleaner (diluted 1:10 with water) and rinse thoroughly with clean water. Before applying a coat of paint, make sure the surface being painted is sound, clean and dry.
Damp protective course (DPC) is seldom installed underneath paving. As such, a high moisture content in the substrate is possible and may cause premature paint failure. Being outdoors, the macro and micro climates that the coating will be exposed to must also be considered. This will help when selecting paint because not all paint will have the same abilities and suitability.
To remove tyre scuffs you can use ProGold General Purpose Cleaner (at a dilution ratio of 1:6) with hot water. Use a soft bristle broom to apply the soap to the surface and rinse with clean water after cleaning. Allow the surface to dry for at least 10 days before applying Prominent Paving Paint using an oval brush.
I am looking for a paintable silicone liquid to paint on to bricks before I plaster to prevent dampness and a solution to mix in the plaster to prevent dampness coming through.
Darryl Watson, by email
Cindy Engels from A Shak replies:
It is not advisable to use a silicone based product as the plaster will not bond to it. There are a number of ways in which you could go about treating the brickwork before you plaster. You could use a rising damp treatment, ours is called DAMPLOC, and paint on two coats before plastering. You could also use a cement additive like TILELOC, which can be mixed in with the plaster (expensive way of doing it), or take two parts cement and one part TILELOC mixed into a paste which can be brushed onto the surface (two coats), creating a waterproof barrier before you plaster.
I found a product in a 2002 or 2003 issue of The Home Handyman called Tufflex and would like to know if the company or product is still around, and, if so, where I can get hold of them as their telephone number no longer exists. The product I recall was used to coat concrete and was very flexible as it would adapt to any movement in the concrete, namely expansion or contraction.
If Tufflex is no longer available, could you advise me on another product that would be suitable? I am in the flooring business so this product information would be of great help to me.
George Armstrong, by email
Perhaps one of our readers would be able to assist, as I have checked the back issue and found nothing about Tufflex. I searched the internet and the only Tufflex is outdoor furniture and decking products, and they never manufactured a Tufflex floor coating. I have also asked many of the manufacturers of building and construction chemicals and they do not know of the product.
There are several companies that manufacture products for this type of application. However, in order to give you the correct solution, you would need to supply more information about the application.
Contact Henkel SA on 0800-138-181 and speak to Rogers Reddy, or try Wayne Smithers at Sika SA on 031-792-6500, or Daniel Fonne at Duram on 0800 500 22.
Painting a timber house
I am sure your experts will be able to guide me in the right direction, with this problem. I live in a house that is mostly wood and, throughout its life, it has been painted with varnish, which progressively darkens with each painting.
I would like to use a colour paint that is flexible to allow for the wood expansion and contraction to make the whole house brighter. What is the right way to achieve this transformation and what other preparation is necessary before the final coat of paint? Also, what paint do you recommend for the final coat, as there are so many brands available?
I live close to the sea, so that may be an issue.
Tony Haley, by email
Frikkie Greeff from Woodoc replies:
I am somewhat concerned with the statement that the “varnish progressively darkens with each painting”. This may be an indication that the old, oxidised varnish is not completely removed before a fresh coat is applied. It is essential, whether paint, sealer or varnish is being applied, that the old varnish is first removed either by chemical stripping or by sanding and that the wood is sanded back to bare, fresh wood. Applying a new surface coating on top of old varnish is like building a new house on old foundations: at some stage the old foundations will fail and that will make the whole system fail.
We strongly suggest that correct and thorough preparation be done first. Thereafter both good quality, organic solvent-based primer and paint, or any of the Woodoc exterior sealers may be applied. The advantages of applying a Woodoc Exterior Sealer are that:
* The products are specifically designed to optimally protect wood in exterior conditions while retaining the natural look of wood.
* No primers need to be applied;
* Woodoc Exterior Sealers are designed to biodegrade and disappear from the wood at the end of their life cycle, therefore obviating the need for deep sanding before renovation. The surface need only be cleaned with mineral turpentine and steel wool before re-applying the Woodoc sealer again.
Please call our toll-free helpline on 0800-411-200 if you have further questions.