Using the right tool for the right job and why it matters – Stuart Downie explores the use of spray gun technology to achieve the perfect finish in a world where first impressions really count.
There are very few places on earth where you can look around and fail to see a coated surface of some sort, many are painted using spray equipment for reasons of speed and finish quality. The expected paint finish quality of a superyacht is unique and unusual in the world of industrial painting. Yacht finishes come under more visual and instrumentational scrutiny than perhaps any other surface finish type you will find in the modern world.
The full coating system on a yacht can be many tens of millimetres in total thickness, yet it is the last 50 microns (0.05mm – about the width of a human hair) which the customer sees and accepts (or rejects). Before this last 50 microns of topcoat is applied, many hours of rectification and sanding are done to filler and primer layers to give a perfect surface for it to be applied onto, but once the topcoat leaves the spray gun, there is little an applicator can do to rectify any problems or imperfections without major re-work, expense, and delays.
There are five things which affect the quality of the application of any topcoat:
A yard can control their environmental conditions, an applicator can control their people (usually) and their processes, the material is controlled, at least until it leaves the factory, by the paint manufacturer and by customer choices and selections, but how much control do yacht paint applicators really have over their spray guns? There are a huge number of variables at play when using spray equipment, which deserve technical articles to themselves. This discussion will address how choosing the right spray gun for yacht finishing could be the most fundamental and basic element of control an applicator can have. Many yacht painters start out as car painters and bring their understanding of spray equipment with them from that industry. Recent times have seen a decline in dedicated equipment-focussed training provided by manufacturers of spray guns and it is worth considering the best way to match equipment to yacht painting applications.
Spray Equipment in the Yacht Market
Yacht topcoats are generally sprayed using air atomising spray guns (usually referred to as “conventional spray guns”, although this can be a confusing term in some situations), with the mixed paint fed at a low pressure, to the gun. This fluid feed can be from a hopper (gravity fed), a pressurised container (a “pressure pot”) or a double-diaphragm pump. The benefits of the different fluid delivery methods are incidental to the finish quality, if managed correctly. The atomisation of the paint by the spray gun is the critical factor. Air atomising guns use a column of air, travelling faster than the paint leaving the gun to break the liquid into small droplets, which are then shaped into a fan by other, smaller jets of air and delivered to the surface. This is a very effective way of atomising a liquid and tends to be the method which delivers the best finish due to the droplet sizes achievable.
Air atomising spray guns are used in a wide range of industries where a good finish is required, the air atomising spray gun market is dominated by car refinish painting, meaning that to some extent, yacht painters have to select their spray gun from a range which was likely designed primarily with car refinishing in mind. Yacht painting is a small market in comparison and therefore is not usually understood so well by distributors or manufacturers of spray guns. It is also worth noting that the finish quality requirements on modern cars is considerably lower than for many of today’s superyachts.
Car refinishing and other industries are heavily regulated and as a result, over the past thirty years, many changes have been made to spray guns in order to meet legislative requirements for efficiency (air atomising spray guns tend to create a lot of wastage and in turn, generate solvent emissions) in those markets. The yacht painting market is not regulated in the same way, the pre-regulation technology would still be acceptable for use and many painters still reminisce about the days when they could use their old fashioned spray guns. This older technology tends to give the best finish, but as the yacht painting market is small in comparison to the car refinishing market, there is little incentive for a spray gun manufacturer to continue to produce this type of equipment.
Another reason that yacht painters tend to use spray guns designed for car refinishing is that, as many painters started their careers painting cars, they bring their spray guns with them into the yacht market. Topcoat sprayers are an elite crew and will tend to have preferences already which may not be questioned.
Of course, the spray guns sold to yacht painters will have been tested with yacht topcoats and will be sold as such, but are they optimised for yacht topcoats, which also remain largely unchanged in formulation technology since pre-regulation spray guns were phased out?
There is one exception. A modern spray gun which uses pre-regulation technology, designed specifically for yacht painting which was created from research and testing carried out in the late 2000s between a leading yacht paint manufacturer and spray equipment company. This spray gun is a technical success, however it will never be the biggest selling item for its manufacturer and therefore receives less marketing input, especially through distributors and a painter needs to know that it exists and ask for it in order to purchase it.
Relatively recently, there have been some yacht painters moving towards electrostatic spray equipment. This tends to be the same air atomising equipment, but imparts an electrostatic charge to the paint droplets which makes them attracted to the surface, which is earthed. Primarily, this technology is used to reduce waste, by having fewer droplets lost to the environment and to help visibility with less spray fog in the painting tent, however other benefits are being claimed by users in the yacht market, such as better finish quality and the ability to apply more paint without runs or sags. These benefits are anecdotal, not well understood and need to be investigated before they can be said to be valid. Electrostatic spraying is an area which is surrounded by misunderstandings and deserves an article to itself in order to expand on the benefits or concerns of the technology. It is also an area which has significant safety considerations and should not be used without specialist advice and training.
Other technologies are seeing growth in the yacht painting market such as air-assisted airless spraying. This is also a technology which deserves further expansion in future articles and has real benefits for some types of materials.
None of the emerging technologies in the yacht market are new, they have been used in other industries for decades and it is therefore possible to understand, optimise and avoid potential problems before they occur with good quality technical support and training.
How to get the best
Before a painter simply asks for the “best” spray gun, they should decide what is the best spray gun for them and their needs. The best equipment is simply that which works best for a specific task in concert with the other four influences of environment, people, process and material. It doesn’t matter whereabouts within a product range a spray gun sits or how expensive it is, the results are all that count.
Larger painting companies often deal directly with the manufacturer and their buying power may lead them to being offered direct technical input and training. This does not mean that this technical support is not available to those dealing with distributors, it’s just not automatic and might be provided by telephone or email rather than a personal site visit. When investing in expensive equipment which has a large effect on the quality of the work delivered, a customer should insist on technical support and training in order to match the equipment to their requirements.
A big investment deserves the time to test potential new equipment with the paint that is being used. It is a good idea to review the whole market rather than relying on a trusted or favoured brand. Take independent advice from experts, seek support from genuine peers and read marketing documents carefully to decide whether any specific gun is actually designed for the job it will be asked to do.
Perhaps most importantly, considering the massive focus on the last 50 microns of a yacht paint system, nobody should ever simply replace like for like, without finding out first if there is something better. It may be that the kit which is currently being used is already the best available for that task, but then again it might not. It could be the difference between being able to give an acceptable finish and an incredible finish.
Yacht finishing is a special and unique area of expertise, yet it remains just one of many markets which spray gun manufacturers sell into. Most manufacturers do not make special efforts to develop specific technology for our needs and it is easy to be sold a piece of equipment which is optimised for a different process. Distributors are not usually experts in one industry and may not have the expertise to solve specific problems in the yacht painting sector, but they do have connections with the manufacturer which should be leveraged when needed. Yacht painting is not subject to the same legislative pressures as general industrial painting or car refinishing and with a little research and some time spent determining what is right for a specific process, buyers can get what they want and, maybe even what they need.
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Stuart Downie joined Safinah Group as a Consultant in early 2020 and has been a technical specialist in the coatings industry since 1995, he has supported markets such as commercial vehicle, aerospace, and yacht as well as spending eight years as Lloyd’s Register’s global Lead Coating Specialist. Stuart has focussed his technical speciality on paint application processes and equipment with unique insight into paint application. He managed aerospace and yacht research spray centres and training schools for one of the world’s largest paint manufacturers and in 2011, he conceived and co-developed a unique spray gun designed for yacht topcoats which remains the benchmark in the yacht painting sector.