Frequently Asked Questions
What are the disadvantages of solvent-based finishes?
Solvent based polyurethane coatings pose severe health risks to flooring contractors, other trades on site, during and after the floor has been coated, and occupiers of the property. These coatings contain high levels of solvents, up to 80%, and chemicals such as Toluene Di-isocyanate, Formaldehyde, Xylene and Benzene. This means they have to be labelled variously as Toxic, Poison and Flammable or at a minimum with Warning and Caution labels. Various studies have associated these chemicals with cancer, nervous system disorders, depression, chronic fatigue, dermatitis, and lung disease. Protector Alsafe, the country’s largest supplier of H & S equipment, will only recommend the use of an independently supplied air system whenever solvent based finishes containing isocyanate are used because the dangers are such that it is not possible to be protected using a normal face mask. The dangers from isocyanate and solvent can persist after the finish has dried whilst it is in the curing phase which lasts up to 14 days, or potentially longer in adverse drying / curing conditions.
In addition to potential health issues there are drawbacks to solvent based products with regard to their appearance and on-going performance. Solvent based finishes are supplied predominantly as gloss finishes as reduced gloss coatings can be more difficult to apply and get good results from. The appearance obtained darkens the floor bringing a yellow tinge and a plastic looking film. As time passes the finishes react to UV light becoming darker with a distinct yellow colour. There is also the potential problem of edge bonding to consider where movement of the timber due to moisture content fluctuation can result in cracks developing in the floor. This occurs where the boards are stuck together due to the solvent based finish penetrating into joints between boards.
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What are the benefits of Bona waterborne finishes?
Bona waterborne finishes:-
- Non toxic and with no hazard classification
- Waterborne and non flammable
- Pose no health risks during or after application
- Quicker re-occupation
- Non–yellowing; no darkening / yellowing of the finish over time
- Minimise the risks for edge bonding
- Maintain and enhance the natural appearance of the timber
- Products available in Gloss, Satin, Matt, flat Matt
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What about VOC’s?
Bona waterborne finishes meet the strictest world standards for Volatile Organic Compounds. All Bona finishes contain less than 100 grams per litre or 9.9% - well within the EU Standard & Green Star requirements. In the case of Prime Classic the solvent content is just 2.3% (25g/Lt).
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Are waterborne finishes more expensive?
The difference between using a waterborne finish and a solvent finish is usually about $4 - $6 per m². However, the many benefits of using Bona non-toxic waterborne finishes far outweigh the dollar cost difference as noted previously.
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What about wear resistance?
Bona Mega can be seen to wear as well as most solvent products and better than others whilst Bona Traffic and Naturale exceed the wear resistance of solvent based products. Practical experience clearly proves that the products can withstand the requirements of domestic and commercial sites. It is important though not to lose sight of the fact that resistance against abrasion is not the only feature of wear resistance. Many companies talk of resistance from Taber Abrasor tests where resistance against an abrasive is measured but this takes no account of scratch resistance, resistance to impact or scuff resistance. Many materials testing organisations such as CSIRO in AU and TRADA in the UK have tried to correlate Taber Abrasion and other tests against on-site real life experience and found that whilst there is a broad correlation it is by no means absolute.
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Why specify a sealer?
Although Bona top coats can be used directly on bare timber, we strongly recommend the use of a Bona Primer as a first coat. A primer is more economical than a top coat, but apart from cost savings there are sound technical reasons to use a primer. Firstly, Classic and Intense ensure the floor has an even look without discolouration or a patchy appearance. Both sealers have significant technical differences that make consideration of the particular installation very important. For example, Classic is recommended to reduce the possibility of edge-bonding. On the other hand Intense is recommended to minimise the effects of tannin bleed on timber species such as Blackbutt. Classic and Intense dry faster than top coats representing a significant time saving.
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What about maintenance?
In addition to the finishes which are available we also have a full range of maintenance products suitable for commercial and lighter use areas. We can assist in developing a complete specification for any contract you may be involved with including advice on preventative maintenance, the choice of finishes and helping to prepare an on-going maintenance / renovation programme.
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How important is design?
The design of a building and its floors can affect coatings and maintenance issues. For instance, in a domestic property the fashion for open plan living brings difficulties in that there can be an issue in keeping a wet edge along a corridor when having to coat individual rooms off of this. Similarly in living, dining, kitchen open plan living areas the scale and layout can prove problematic. Having thresholds at doorways separates areas and allows individual areas to be coated more easily. Similarly in commercial areas, whilst it is clear that some areas need to be maintained as a single large floor area, by trying to keep sections within some premises to perhaps 100 or 200m² this allows commercial premises to continue to function and trade whilst sections of flooring are overcoated as part of normal maintenance operations.
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What is edge-bonding?
This is a potential problem where movement of the timber due to moisture content fluctuation can result in cracks developing in the floor. It occurs where the boards are stuck together due to a finish penetrating into joints between boards. Typically up to 10 or so boards are stuck together. When they shrink rather than each joint between the boards opening up the shrinkage for the whole area is seen at a single joint, where the adhesive bond is weakest, and this may be over 10mm. In some cases the adhesive bonds at the joint are so strong that the timber itself breaks and a crack develops along the length of a board. Waterborne finishes have a lower tendency in general to give this type of effect and Bona have developed products where they specifically engineered the finishes to minimise edge bonding. For this reason it is strongly recommended that a Bona Primer is used prior to application of Bona finishes.
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What is ‘tannin bleed’?
This is a discolouration that occurs with some timber species containing high amounts of tannin, especially Blackbutt. After the second coat has dried the effect is seen as a green, blotchy or blurry look. Sometimes the finished floor can still be acceptable, but often the floor needs to be sanded back to bare timber and coated again. Always use Prime Intense when coating Blackbutt or other high tannin timber species.
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