Having the correct set-up is vital for achieving a quality paint finish. Here’s what you need to get started if you want to respray your classic Ford.
The spray gun
Your spray gun must be suitable for the job and the paint being used. Nozzle sizes – for example 1.8 mm – give some indication as to the types of paint and achievable finish. A 2 mm nozzle is suitable for high-build primers, whereas a 1.4 mm nozzle is suited to top coats and lacquers. Specifications vary so it’s important to understand the link between nozzle size, paint type and quality of finish.
Hoses come in a variety of bore sizes, typically 8 mm (0.25 inch) for suction and gravity-feed guns and larger bore for HVLP guns. Check the spray gun specification and compressor output for the optimum size. If your compressor’s housed outside the spray booth, you need to allow for air pressure drop, which increases according to the length of the hose. A drop of 0.47 psi per foot at 50 psi through 8 mm hose at 8cfm is a good working guide, although this drop will increase to more than 11 psi on a 25 ft hose. For best results, always measure air pressure at the gun, not the compressor.
Personal Protection Equipment (PPE) is essential when spraying. Long-term health problems can be avoided by using appropriate clothing and suitable respiratory protection. Overalls should cover all bare skin. Lightweight disposable versions with elasticated cuffs are best for movement, ease of use and their anti-static properties. Latex or nitrile disposable gloves must be worn at all times. Two-pack paints require the use of an air-fed visor mask. This is critical because airborne particles fed into your lungs will chemically harden and remain there. Your body cannot remove accumulated isocyanates from itself. A suitably sized compressor with the correct filter unit will be able to power a suction-feed spray gun and an air-fed visor mask. If spraying cellulose outdoors, eye protection plus a mouth and nose mask suitable for paint vapours should be worn, never a cheap dust mask. Cover your head and wear eye protection to minimise the risk of further health problems. We don’t condone spraying any paint type without the necessary PPE.
The area shown is a professional spray booth capable of housing a bus. For the DIY sprayer, it’s possible to turn your home garage into a temporary spray booth or spray outside if conditions are right. All paints have a working temperature in which they perform best. Extremes of hot and cold must be avoided. A stable temperature is required. Good lighting is essential to see what you’re spraying. The spraying area must be as dust-free as possible without oil and silicone contaminants in close proximity. Plastic sheeting to line the walls and floor is one solution. You must have ample room around the item being sprayed to work comfortably without snagging air hoses and overalls on your fresh paint. Consider any health or injury risks to neighbours, family and pets.
The spray gun being used will have a cubic feet per minute, or cfm (sometimes cfpm), rating. This is a measurement of how much air’s fed by the compressor past its outlet valve in one minute. The compressor must be capable of delivering a constant flow at the gun’s specified rate, for example 8cfm. Failure to have a powerful-enough compressor will result in poor atomisation of the paint and poor application. High-velocity low-pressure (HVLP) guns require much larger compressors to power them even though they spray at much lower gun pressures than standard spray guns.
Test panel set-up
Jason Charleston from S&B Automotive Academy showed us this clever set-up trick for all spray guns. Set the fluid adjuster to its closed position. If it has no markings, stick some masking tape over it and mark it closed. Do the same with the fan width adjuster. Secure a large piece of masking paper to a vertical surface and mark it from 0 to 4.5. Turn the fluid adjuster half a turn at a time and spray a small blast of paint into the appropriate marking. Once you’re happy with the paint flow (good coverage without any runs) do the same with the fan width adjuster. A smooth feathered-edge fan as wide as possible is best for panel work. Jason chose 4 flow and 2.5 for fan adjustment on the example shown. Now you can work confidently knowing what your gun will do when its trigger’s fully pressed.
Using the compressor
Keeping your compressor in top condition is necessary for achieving satisfactory spraying results. When in use, it should be checked daily for moisture by opening the moisture drain taps and draining the water. Water vapour occurs as a result of the air being compressed. Drain taps are found on the lowest point of the compressor tank. Some air regulators also feature drainage taps. These should be opened at least once a day when in use. If the spraying equipment isn’t at the same temperature as the ambient spraying temperature, make regular checks for moisture before you spray. If left unchecked it’ll corrode the inside of the compressor tank – the corroded metal and moisture can end up as part of your superb paint job.
Keep your distance
Jason then demonstrated how to maintain a consistent distance from the workpiece by spreading his hand to eight inches wide and holding it between the panel and the gun. He did this every time before he began spraying a panel. The gun should be moved across the panel by moving your whole arm steadily to maintain distance and angle, not just your wrist.
A meticulous cleaning regime is needed to ensure your spray gun will give consistent results every time you use it. You’ll regret being lazy with this next time you come to start spraying. Two-pack paints, for example, dry by chemical reaction, meaning they usually have to be used within 10-20 minutes of being mixed. This is known as their pot life. Hardened paint can quickly ruin a spray gun, so be thorough. The golden rule is to strip the gun from back to front and then refit the components from front to back. This means the needles are refitted last to avoid damaging them.
This classic Ford tech guide on how to respray your classic Ford first appeared in the March 2018 issue
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