Says Steve Louis, Sales & Marketing Manager, HMG Transport Coatings Division

When spraying large vehicles, size clearly does matter, but so do many other factors that should be taken into consideration in the pre-planning of any paint job. Large vehicles are usually complex shapes and they usually involve different substrates, multiple colour schemes to achieve corporate livery standards and, complicating matters even further, a variety of application equipment and operator conditions; spraying and curing facilities, as well as drying temperatures, also play a major role in the planning stage.

When considering a large paint job, it is also important to understand the consequences of your decisions; for instance, choosing a fast hardener and thinner may give you quick drying times, but the downside is poor wet edge times and, in consequence, a dry dull finish. The primary objective is always to achieve the best aesthetic finish in a reasonable amount of time, within the confines of a labour and materials budget, bearing in mind that rework on such large vehicles is an absolute no-no.

Technical paint knowledge is sometimes no substitute for practical experience either. What is in theory the best system to use, may not turn out to be the case in practice. Our customers prove that to us time and time again; after all, they are the expert applicators.

Here then are some of the key points to consider, when spraying large vehicles:

Colour Matching

First, always take time to check that you have either mixed up, or been supplied with, the correct colour. Spray out a test panel first, then check it against an approved standard or have the vehicle owner approve it, since repainting a vehicle due to a poor colour match is a very expensive pastime.

Application Equipment

Unlike car refinish work, commercial vehicle refinishers have a whole range of application equipment to choose from, including conventional hand-held gravity or suction HVLP, pressure-pot HVLP, diaphragm pumps, air-assisted, airless and electrostatic technology. Each has its own advantages, according to the substrate type, size, shape, material to be used and desired finish, so equipment manufacturers should be consulted in order to maximise potential. In my opinion, the industry sometimes fails to take full advantage of this free expertise, especially since choosing the correct equipment can make the difference between poor, good and absolutely first-class paint jobs.

Hardener / Thinner

The choice of hardener/thinner is one of the most critical factors and needs to be made based on vehicle size, spraying temperature, application equipment and the number of operators likely to be spraying at the same time. It is always best to use the specific hardener and thinners recommended by the paint manufacturer, since these have been developed together in order to offer the best performance balance and will work in complete harmony with one another.

Curing Times

At HMG Transport Coatings, we have a range of hardeners and thinners to suit different temperatures and, if in doubt, we always suggest opting for the slowest system available, when spraying large vehicles. Contrary to common belief, this will not slow down through-cure and will give you plenty of wet edge time, leading to ease of application and optimum finish. Spraying large vehicles tests one’s fitness enough, without having to race around like Linford Christie to maintain a wet edge, so let the system work for you. What’s more, through-cure and finish are often at their best when using slower systems.

Topcoat System

By far the best topcoat choice for refinishers and fleet owners are high performance 2K acrylic systems. Although slightly more expensive than the traditional alkyd polyurethanes used historically, their workability, drying times and overall performance make these 2K products the new industry standard. Moreover, with the latest environmental legislation specifying the use of a topcoat system with no more than 420g/l of VOC, this is probably the easiest decision to make, as it’s effectively made for you.

Multiple Colours

Dependent on the colour scheme, you could use either a solid direct gloss or a solid basecoat with a clearcoat over the top, even a combination of the two systems. Whilst the clear-over-base system has long been popular, the advent of waterborne basecoats means the industry is facing new challenges in perfecting the application of this new technology. Either way, remember that the ancillary products available for each refinishing system are there to assist you in achieving the optimum finish, in the fastest process times.

Masking Products

Masking products are very important whichever system is employed, particularly when applying multi-colour liveries. The use of incorrect tapes, papers or polythene sheeting can damage fresh paintwork beyond recovery, resulting in expensive rework, so don’t cut corners in this area.

Drying Times

Remember, the drying times presented on technical data sheets are theoretical and are typically based upon metal temperatures. So a key point to consider is whether the vehicle is constructed from steel, aluminium, GRP or another form of plastic, as each will absorb heat differently. Twenty-gauge steel will heat up quicker than a big chassis rail, for example, and will absorb more heat than GRP or plastic and retain temperatures for different lengths of time. Also, whilst the data sheet may advise baking at 70ºC for 30 mins, it may be half an hour before the vehicle is actually up to temperature, so that has to be taken into account too.

Finally, when spraying large vehicles, it is always best to take time at the beginning of the job to plan the whole process. Just because it’s the same type of vehicle you painted last week, are the circumstances exactly the same? Is it one colour or multiple, how many staff are available, which primer system is best and what value is involved in the job? Then ask yourself how well did that last job go and can your work be improved upon? Also, don’t overlook the advice and expertise freely available from your suppliers, in terms of paint selection, prep materials, application equipment, training and best practices, all of which will help you produce the perfect finish. After all, size isn’t everything, it’s the complete package that counts.

HMG Paints is drawing upon its strengths as the leading supplier to the UK bus & coach industry and a growing presence in the CV refinishing sector, to launch a one-stop coatings solutions network for the Commercial Transport industry. Based around its programme of high performance paint systems and to be branded Network CT, the combined product and service solution will offer bus and coach operators and CV fleet companies, especially those without in-house paintshop facilities, an exclusive network of approved CT repairers, refinishers and bodybuilders, backed by specialist paint distributors and providers of associated application equipment, products, service and training. Network CT was unveiled at Britain’s largest road transport event, the Commercial Vehicle ’07 Show at the NEC, where HMG market specialists introduced the concept to vehicle owners, repairers and suppliers and explored the benefits and requirements for each membership category.

Britain’s leading independent paintmaker also used the CV Show to preview a number of important new high performance CT coatings, including a new version of its market-leading 2k topcoat system, called Acrythane XSC Advance, and a family of water-based 42/CE compliant products for the transport industry, named Hydroline. These products are currently being trialled and tested by specialist users across the industry and will be ready for national launch shortly.

HMG Paints, through its network of independent CT product distributors, supplies many leading vehicle manufacturers, bodybuilders and repairers, bus operators, tanker fleets, logistics companies, trailer manufacturers and rail companies, in the process building up in-depth knowledge of the technical, application and finish requirements that are singular to the transport industry. Painting commercial vehicles is quite a different proposition to passenger cars, from the size of panels and wide variety of substrates, through the use of multi-striping and vinyls, to the need for a high gloss finish that can withstand severe scrapes and knocks, as well as daily mechanical washing. So the coating systems, the methods of finishing and refinishing, sometimes involving brush painting, and the paintshops themselves are highly specialised, requiring a quite different market approach.

That is the thinking behind HMG’s Network CT scheme, which will ensure paint products and processes that deliver maximum performance and durability, exact colour matching to corporate liveries, and the high standards of paintwork quality and finish the industry and its customers demand. There will be four membership categories – Owners/Operators, Repairers/Refinishers, Paint Distributors and Associate Suppliers – and the scheme will be distinguished by branded signs and point of sale material.

For fleet owners and operators, large and small, Network CT will offer an identifiable banner, under which they can access the specialist transport coatings knowledge that will ensure a first-class finish every time, at the same time contributing to enhanced fleet value and a positive brand image. Tailored paint specifications, including undercoating systems and colour references, will be drawn up by HMG and made available to designated Network CT repairers, refinishers and paint suppliers, ensuring all finishing and refinishing is carried out to an agreed standard.

Network CT paint distributors will be approved under the scheme, as offering the level of product knowledge, customer service, delivery flexibility and technical back-up demanded in the transport coatings sector. Commercial vehicle repairers and refinishers will be appointed through a detailed selection process and will benefit, in turn, from a direct link between identified work sources and an unrivalled CT coatings knowledge base and supply network, provided by HMG and its distributors.

Associate members, such as equipment and training providers, will be able to market their services within a network of transport industry professionals, at the same time extending the nature and scope of the Network CT one-stop solution. Information about the scheme and contact details for all members will be accessible via a dedicated password-protected website and the domain name www.networkct.co.uk has already been reserved.

Technical, safety and application specifications for all HMG’s CT coating systems and previews of new product introductions will also feature on the site. Among the first to be featured will be the latest generation of the company’s renowned Acrythane 2K acrylic topcoat, Acrythane XSC Advance. An ultra high solids formulation, it employs the latest resin and pigmentation technology to meet <420g/l VOC requirements, whilst continuing to offer such outstanding properties as extremely high gloss levels, rapid drying even at low temperatures, reduced process times and long-term durability in the harshest con

With the implementation of stricter VOC regulations, demand for waterborne coatings systems is set to grow and HMG is applying its paint manufacturing and R&D skills to formulating a complete new family of water-based products, HydroLine, designed for commercial vehicle applications and yielding inherently low emissions. First up is HydroBase, a waterborne transport basecoat system, available in a full range of colours and metallics, which fully complies with EU Products Directive 2004/42/CE when used in conjunction with a recommended HMG 2K-compliant clearcoat; other water-based products in development include HydroPrime, HydroCoat, HydroThane and HydroGuard. HMG will support these new lines with up-to-date technical advice on production application, spraybooth atmospheric control, air movement and product storage.

For further information about Network CT and the new transport coatings, contact HMG Paints, Riverside Works, Collyhurst Road, Manchester M40 7RU, telephone 0161 205 7631, email sales@hmgpaint.com