Crack repair - Weathercrete and Joint Sealer

I have, in separate posts, dealt with the repair of cracks using both Weathercrete and Joint Sealer.
Weathercrete is a "twin-pack" material comprising of a pre-weighed, dry cement component, mixed immediately prior to use with a liquid polymer. The resulting repair plaster has very good adhesion to a variety of substrates, is water-proof, highly abrasion resistant, and has a good degree of flexibility. Thorough mixing on site prior to use is a problem in some cases, as mechanical stirring is advised. More and more of our regular contractors are opting to use Joint Sealer - a high volume solids acrylic, rather than Weathercrete, to fill cracks on walls. Weathercrete remains the product of choice for repairs on floors, however, where abrasion resistance needs to match that of the surrounding substrate.
On walls, both repair materials should be over-coated with two coats Elastocryl prior to the application of top-coats, so that the necessary film thickness is achieved to permanently seal the crack.

Single and Twin Pack Etch Primers

The priming of non-ferrous metals became an issue during World War 2 when aircraft and ships were starting to be built using aluminium rather than the heavier steel previously used. The U.S. military claim the original development of etch primers and their introduction into the coating industry. Phosphoric acid, when added to paints based on phenolic/polyvinyl butyral resins provide the adhesion required to successfully coat 'difficult' metals. Anti-corrosive pigments such as zinc tetroxy chromate were used to provide the protection against corrosion.
After the withdrawal of calcium plumbate, and chromate pigments from the market due to health risks attached to their use, etch primers have been more and more popular, not only for priming non-ferrous metals, but as the first choice in primer for ferrous and galvanised metals as well. The solvent blend used is rich in alcohols, making the coating quick drying. The product can be applied by spray  as well as by brush or roller.
As a rule, in the South African coating market, single pack etch primers are applied to galvanised iron or ferrous metals, and twin pack etch primers are applied to non-ferrous metals (mostly aluminium or stainless steel), usually by spray application. Twin pack etch primers have, in addition to this, been very successfully used to prime glass-fibre substrates for subsequent coating.

Dealing with crazy-cracking

Under certain conditions, new cement plaster hardens with a hexagonal pattern of very fine cracks present, roughly the size of an adult's hand. These are not visible to the eye, but if a solvent based bonding liquid is applied to the surface, their presence is shown very distinctly. As things stand there is no special coating requirement, and the usual one coat of a Masonry Primer and two coats of a good top-coat will suffice. A big problem, however, arises when these cracks open and close under large temperature changes or settlement of the new structure.
The very standard coating procedure given above will provide up to 100 microns of top-coat. When these cracks open - often as much as 500 microns, huge stress is applied to the dry paint film above the crack. Upon stretching to accommodate the crack below, the paint film above it becomes thinner, much like a rubber band would if stretched. For a paint film to accommodate that type of stress, not only does it need to have an intrinsic degree of flexibility, but there also needs to be enough film thickness to allow that type of elongation without the film breaking above the crack.
The leading  international Pure Acrylic binder manufacturer conducted a series of tests to determine the film thickness required to successfully bridge opening cracks of this nature. Not surprisingly, the binder had to be of a highly flexible nature - but what was surprising was the fact that a minimum film thickness of 320 microns was required to survive the ordeal. This would require around 7 coats of most top-of-the-range pure acrylic exterior coatings currently used in the South African paint market. I have never seen a specification calling for 1 coat Masonry Primer and 7 coats pure acrylic top-coat before!
Should you need to re-coat a wall where crazy cracking is evident, after surface preparation, apply one coat Plaster Primer, followed by two coats Elastocryl ( a fibre re-enforced, high solids, pure acrylic coating) at 5 square metres per litre before coating with two coats of the chosen top-coat. Better still, contact us for advice specific to your job's requirements.

Repairing of plaster cracks - Weathercrete.

As part of surface preparation, when repainting plastered surfaces, cracks are often an issue. Hairline cracks can be sanded to a smooth profile, spot primed with Plaster Primer then over-coated with two coats Elastocryl prior to recoating the wall. The two coats Elastocryl will give 210 microns of film thickness, before the top coats are applied. The total film thickness over the crack will then be sufficient that should the crack re-open due to movement of the substrate, the paint film above it will not break.
Larger cracks should be raked or angle ground open, to a sound substrate, before re-filling. Here we recommend the use of Weathercrete -  pre-weighed cement to be mixed with the polymer supplied, to be used as the fill compound. The resulting profile of the dry fill will match the surrounding plasterwork to a far greater degree than when using cellulosic fillers. Patting the surface of the still wet filled area with a damp sponge helps to match the surrounding plaster profile. Once this is dry, spot prime the repair with Plaster Primer, over-coat the repair with two coats Elastocryl and proceed with the application of top-coats.
Weathercrete can be used to fill plaster defects on cement floors, as a waterproof grout between tiles, or even as a tile adhesive. Be sure to clean the equipment used with water directly after use, as once dry, the adhesion to metal is so good that you may have to angle-grind it off.

Twin Pack Epoxy and Polyurethane coatings

Twin Pack Epoxy and Polyurethanes are extensively used in industrial applications. Most of the volumes sold of these two products are used for flooring or coating of machinery.
Twin Pack Epoxies, in general, have better solvent and chemical resistance than the Twin Pack Polyurethanes. They have better adhesion to metals, and again, in general, have better abrasion resistance than Twin Pack Polyurethanes. They are also cheaper than their Polyurethane counterparts. Their chief draw-back when compared to TP Polyurethanes is their very poor u.v. resistance - making them suitable only for interior coating applications.
Twin Pack Polyurethanes can be used for demanding out-door applications such as the coating of boats, trailers, automotive coatings, aircraft, trains etc.
Both options have similar surface preparation and curing requirements, and both require a level of expertise to use. Always check with the supplier before using these products as to their suitability for your requirements, and obtain a detailed specification for the application. When used correctly, both products can provide many years of protection.


Fruit packaging warehouse floor - Twin Pack Epoxy

Workshop floor - Twin Pack Epoxy



Wood-floating of cement floors

Very often we are called out to give advice on the coating of cement floors. The proud new owner of the building shows us the power- floated floor. Many times the floor is as smooth and shiny as a mirror. Unfortunately this is not ideal for coating, as the surface has been rendered totally impervious to coating penetration. The first step required in term of surface preparation is then to roughen the surface so that it resembles 100 grit sand-paper. This will ensure good adhesion and penetration into the substrate, and prevent the coating delaminating from the substrate. Impact of a heavy object falling onto the coated surface, or a vehicle - even a pallet-jack – turning sharply, can cause the coating to come away from a very smooth surface if no penetration has been possible. The best method of roughening a smooth surface is by floor grinder. These can be hired by the hour from construction equipment hiring businesses. They create a lot of dust, but do the job very well. It is best to vacuum up the dust using an industrial vacuum after this process is complete. Ensure that the entire floor, including edges right up to the walls and hollow spots, are evenly abraded.

An alternative method is to acid etch the floor, but the drawbacks far outweigh the reduced cost of this approach. Strong acids are hazardous chemicals and should never handled without the correct training and Personal Protective Equipment. Acid fumes generated are highly corrosive – both to the applicators and to electrical distribution boards. The acid tends to lie in hollows on the surface, leaving high spots untreated. The floor needs to be rinsed off after etching – leaving it wet and therefore unsuitable for immediate coating. We do not sell acids used for this application due to these limitations.

 

Below is a photo of a floor topping being wood trowelled for later coating.

 

The moral of the story is that if you are screeding a floor that will be coated at a later stage, save yourself some money and have it wood-floated to a rough finish.

Coating of polystyrene ceiling panels

More and more ceilings boards and cornices being installed these days are made out of polystyrene. They are light-weight and easy to mould into fairly intricate cornice designs. Not only are new ceilings boards often made of polystyrene, but there are a large amount of industrial buildings where thick (75mm) panels were used to form dropped ceilings - both for insulation and sound dampening considerations. Some of the older ceilings we have seen in wine cellars have been so contaminated with fungal growth that we have advised the client to replace them rather than trying to sterilize and coat them. Coating of these panels - after sterilizing with Fungal Wash, if required, is a simple process. Ensure that the product to be used is water-based and you can simply apply two coats by conventional means. Any aromatic solvent containing paint cannot be used, as the polystyrene will dissolve.

Elastocryl - quick drying waterproofing system

Elastocryl was developed at the request of local waterproofing contractors to provide a product that can be used throughout the year - including wet and cold winters. After doing our research into what was being used elsewhere in the world, with similar climates to the Western Cape, we had a starting point to work from. Laboratory produced samples were tested by contractors, fine tuned after feed-back, and we were up and running.
The success rate of this product has been phenomenal - we receive many calls from satisfied customers telling us how Elastocryl worked where many attempts with other products have failed. Essentially it is a high Volume Solids adhesion promoted pure acrylic, re-enforced with a high loading of wood-fibre. It dries a lot faster than other water-based waterproofing coatings, and can be applied with rain only hours away.
Possibly the best testimonial we have received was from the owner of a dedicated paint outlet - one of our opposition - who successfully waterproofed their own shop roof during light drizzle. Their own product had failed - even though it was applied in good weather conditions. Needless to say they now sell Elastocryl very successfully in their area, even though it is produced by an opposition manufacturer.
Elastocryl can be used with or without a polyester membrane, depending on the application. Application of two coats of Elastocryl at 5 square metres per litre to badly hairline-cracked substrates, followed by the top-coats, has rendered many buildings free of moisture ingress. Sealing of parapets, 'flat' concrete roofs, even reservoirs and ponds, have all been successfully achieved by this product.

Give us a call before your next waterproofing challenge - Elastocryl will beat it!

Druiwebak Verf - literally Grape-bin Paint

This is a versatile product made to coat metal bins that harvested grapes and fruit are transported in.
It is a quick drying solvent based coating, resistant to acid and alkali, self priming on metal and has low moisture and oxygen permeability. That is quite a list of attributes for a single product, and is what makes it so versatile. Low moisture and oxygen permeability reduce the chances of the substrate rusting and together with the inclusion of an anti-corrosion pigment, make the product a good choice as a metal coating. Resistance to acids, self priming on metals, low oxygen and moisture permeability, and good u.v. resistance makes it ideal for the primary use on grape/fruit bins. The fact that it is alkali resistant makes it suitable for coating directly onto cement plastered surfaces. Walls and floors in wine cellars and fruit pack-stores have been successfully coated with this product. The binder composition is similar to that of the traditional road-marking paint - the ones that lasted years but are now deemed to be too expensive.
The photo below is that of a wall in a wine-cellar, subsequently coated with Druiwebak Verf, after sterilizing with Fungal Wash.

Druiwebak Verf has Thales approval for use in wine-cellars.

Primers and undercoats

Primers, be they metal or wood primers, are formulated to be in direct contact with the raw substrate. When preparing a surface for repainting, one of the requirements is to scrape off loose or flaking paint . When the prep work is complete, and the substrate has been exposed in discrete areas, that particular area needs to be spot primed with the appropriate primer before recoating. Many times we see metal primers being used over the entire surface of previously painted metal or wood objects, before the object is repainted. Anti-corrosive pigments, used in metal primers, need to be in contact with the metal substrate for them to be effective. Similarly, oils in wood primers need to be in contact with wood for them to lubricate wood fibres.
Plaster or Masonry Primers are alkali resistant, breathable coatings designed to penetrate and bind the upper layer of a plastered substrate. Often we see contractors using "Universal Undercoat" in place of Plaster or Masonry Primers, often with disastrous consequences. Universal Undercoat's are not alkali resistant, and should only be used over primed surfaces. They contain neither anti-corrosive pigments, nor wood-fibre lubricating oils, making them unsuitable for use directly onto metal or wood.

Coatings for Mass Housing

Mass housing development is huge in South Africa, and most other African countries. In the Western Cape, all exterior coatings have to carry an Agrement Certificate. This ensures that the product will effectively seal and protect the structure, and have an acceptable life expectancy. We have been supplying coatings for mass housing for may years, and have formed good relationships with our clients. By getting involved in identifying potential design problems we have been able to eliminate many water-proofing and coating issues, thus saving the client both time and money. Joint Sealer (see previous post) was developed specifically to deal with a problem on a large mass housing development, at the request of the client. The notion that cheaper housing will use cheaper coatings is false - in many ways the coating requirements are more demanding than those used in the 'conventional' housing market. Taking a hands on approach to technical service on mass housing sites has taught us a lot about practical building methods, and has put us in a position to provide coating solutions to diverse application challenges. The two photos below give an indication of the scale of the projects. Both of these projects involved supplying the coating requirements for over 2000 units.

Weatherklad - Heavy duty exterior protection.

Weatherprufe Weatherklad is our flag-ship product. It is an adhesion promoted pure acrylic, formulated with high volume solids for thick film protection. The product is fibre re-enforced for crack bridging and tensile strength, and contains a dry film fungicide for protection against mould and algal growth. Many projects, from sea-side homes and apartments to farmsteads in the hot Western Cape interior, have been successfully coated with this product. We produce the coating in a range of colours for exterior walls, or tinted to the colour of your choice,  as well as in oxide shades for use as a roof paint. A variant of this product, Cellarklad, containing the maximum recommended level of fungicide has Thales approval for use in wine-cellars. Below is a photograph of a recently completed project in Cape Town, where Weatherklad was used as the exterior top-coat.

Polarsheen - Low temperature curing acrylic

Polarsheen is a pure acrylic water-based paint formulated to dry at very low temperatures. It has Thales approval for use in wine-cellars. It has been successfully used, over a period of several years, in Controlled Atmosphere Rooms (low temperature and reduced oxygen storage rooms where fruit is stored) across the Western Cape. The product has low odour and is able to dry at temperatures below 4 degrees Celsius. Flexibility is very good resulting in the product being used to seal the gaps between panels in Controlled Atmosphere Rooms. The photograph below was taken in an underground wine cellar coated with Polarsheen. The product also contains a dry-film fungicide, to prevent mould growth.

Wood varnishes and wood seals

Protection of exterior wood can cause a lot of head-aches if the right route isn't followed from the outset. Often the quality of wood used in South Africa is not the best, and this only adds to the problem. If new work is being done, start off by using the best timber you can afford. Hard, dense woods are more dimensionally stable than softer woods, and the additional cost is money well spent.  Harder woods are less porous than soft woods, meaning there is less swelling due to water ingress, and ultimately less chance of rotting. They are also less prone to warping due to heat - both of these factors lead to less stress being placed on the coating, from factors other than uv light and the elements. Having installed the timber, check with the timber supplier whether the density is suitable to be coated with a varnish, or a wood-seal, as very dense timbers should only, at the most, be protected by a wood-seal.
Preparation of new timber involves sanding the surfaces to be coated to a smooth finish and removing dust. Knots (if present) should be sealed using a knot-sealer as per the manufacturer's instructions.

• Varnishes are typically solutions of long oil-length alkyds (a solvent based binder type) containing a low level of Linseed Oil ( to lubricate the upper-most wood fibres). Other additives could include u.v. absorbers and transparent iron oxide colourants. Typically this finish is glossy. The coating will have a limited penetration into the timber - so thinning the first coat up to 10% with Mineral Turps is advised. Allow this to dry for 24 hours, and thereafter apply the first of two top-coats (unthinned) with 24 hours between coats. Maintenance of these coatings would involve sanding the coated timber to an even, matt finish, and re-applying one unthinned coat every 12-18 months.
• Wood-Seals are dilute solutions of long oil-length alkyd, with a higher level of Linseed Oil, and waxes. The same additives are used as for the varnishes. There is generally more penetration of a wood-seal into the timber than varnishes, and the product has a matt, waxy appearance. They take longer to dry - due to the higher Linseed Oil level, and for this reason are seldom used indoors. Three coats can be applied (at 24 hr intervals) to the prepared timber. Maintenance of these coatings involves cleaning the surface with a rag soaked in Lacquer Thinners, allowing to dry, and recoating. Maintenance intervals are the same for each coating type.

Twin Pack Epoxy Coatings

It has become very fashionable over the last few years to have coated cement floors in office entrance halls as well as in kitchens and bathrooms in domestic homes. These floors are often coated with Twin Pack Epoxies. A problem can arise when the interior design calls for colours produced from blends of different pigment types. Epoxy resins are ideal for the production of industrial coatings, where performance is more critical than aesthetic attributes. Pigments are not well stabilized in such resins, and preventing different types of pigments from floating is a problem associated with these coatings. I saw a problem created by the floating of pigments during roller application to a floor that can be directly attributed to the tinting of a medium grey shade to a blue-grey colour. Due to different pressure applied by the applicator, roller width stripes of noticeably different colours were evident in some areas. Murphy's law reigned supreme in this case, and the darker stripes were in the middle of the floor. A third coat, carefully applied, sorted the issue out. Fortunately, this was a small area that had been coated, and the applicator had enough product left over to complete the repair coat.

Tornado Degreaser

Tornado Degreaser is a water-based highly concentrated multi-purposed product that has had a lot of success in diverse applications. It has approval for use in wine-cellars (via Thales Institute) and cleans the exterior of old wine tanks back to bright metal. Diluting the product anywhere up to 20:1 with water allows it to be used as a household tile cleaner, wall cleaner, pre-soak for oily clothes (reportedly even bloody clothes after a hunting trip), pot cleaner amongst others.
More paint related uses include degreasing of new galvanized iron roof sheets, removal of oil patches from workshop floors and degreasing of metal objects prior to coating. The water-based formulation makes the product safe and easy to use and results are excellent.
Copper stains in old enamel baths and iron stains on boundary walls from bore-hole water are no match for the product either.

Painting of boundary walls

Correct procedure for this application will ensure maximum life span of the coating. Very seldom are boundary walls constructed with the inclusion of Damp-Proof Course (DPC). This means that the lower part of the wall will be subject to rising damp. Watering of lawns and flower beds adjacent to the walls provides a constant source of water around the base of the wall causing this to be a constant issue. Here's how to deal with this in the best possible manner.
Remove all loose and flaking paint by scraper. Cracks, if present, should be opened up by angle grinder. Refill these areas using a 3:1 sand/cement mix using Weatherbond Enhance (a water-proofing polymer) to wet the mixture to application consistency. Using a sponge, remove excess and match the appearance of the repair plaster to the existing profile surrounding the repair. Allow this repair to dry for 24 hours. Spot prime repairs or any exposed raw plaster Using Plaster Primer and allow to dry for 8 hours. Treat any fungal/algal contamination by application of Fungal Wash - allow 6 hours for the product to sterilise the surface and then scrub or high pressure jet the debris of the wall. Re-apply Fungal Wash and leave to dry on the surface - do not wash this off before re-painting.

Water-proof the top horizontal surface, or coping, by application of two coats Elastocryl, at a spread rate not exceeding 5 square metres per litre, allowing two hours drying time between coats. This area can then be coated with two coats Weatherklad in approved colour ( 8 square metres per litre, 4 hours drying time between coats). This will eliminate the possibility of water-ingress from the top of the wall, leaving only the issue of the rising damp to be best accommodated.
The vertical surface should be coated with two coats MattCoat 40 - a breathable matt finish product.
This will ensure moisture rising in the wall has the greatest possibility of diffusing through the coating, in the form of water-vapour, without damaging the coating. MattCoat 40 is also a far cheaper product than sheen finish alternatives - it is not often that the best technical option also costs less!!

Paint store audit and advice

Maintenance Managers on wine farms, fruit farms, and in the fruit packaging industry (as well as food and beverage suppliers) are tasked with maintaining the standards required for regular audits and inspections related to accreditation for supply to the local or international markets. Budgets for the required maintenance are often limited and the need to get the full benefit out of money spent is obvious. In many cases we have seen paint stores containing several half used paint cans, often produced by several different manufacturers, lying idle and collecting dust. Putting these products to use before re-ordering could save a lot of money.

A service we offer is to check the viability of the products currently stocked in terms of stability and suitability for use. This involves the identification, determination of viability, re-labelling if necessary, re-sealing and recommendations in terms of areas that can be coated with the product concerned. This results in substantial savings and leaves you with easily identifiable products – and a tidy store, at no cost to you.