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Paint Spraying - The Basics
Paint Spraying Step by Step Guide step by step guide     Back to Spraying & Painting back to spraying & painting

Paints and Surface Preparation     Organising the Work
Thinning the Material   Cleaning Up
General Techniques Troubleshooting
Spray Painting Mechanics    Thinning & Mixing Guide


The Basics

Once the compressor system has been set up paint spraying can then be undertaken. To achieve a smooth even coat the gun and the material must be prepared and thinned in accordance to the manufacturer’s guidelines. The gun must be clean and properly loaded, the airflow and fan pattern adjusted and the compressor set at the correct pressure.

It is recommended to make a note of the thinning ratio & to run one or more test on a similar surface before starting with the actual project.


Paints and Surface Preparation

hammerite paints Hammerite Paints - www.hammerite.com

A very useful web site giving detailed information on the types of paints, and advice on surface preparation on a lot of spraying jobs.

diy data UK DIY web site - http://www.diydata.com

General Techniques

Now that the material is strained and loaded and the gun is properly adjusted; you are now ready to spray. Using a spray gun is not very difficult providing a few techniques are followed. Plenty of practice is required before pointing the material at an expensive or delicate piece of furniture.

To achieve a smooth even coverage follow these simply guidelines which appertain to any piece of work:

Where possible place the work on rollers or a turntable so the same spraying position is maintained throughout. If this is not practical place the piece of work in a position where minimum repositioning of the work is needed. For example when spraying a pine chair, place this in an elevated position so that all the surface areas are accessible without moving. Hold the gun perpendicular to the work surface at all times and at the same distance from the work for the entire “pass”. A “pass” describes the action of spraying from one end of the work to the other where a series of passes is needed to complete the entire piece. Again it is advisable to practice these techniques on waste wood, cardboard or paper first.


Spray Painting Mechanics


spray painting mechanics When spraying move your arm in a wide sweeping motion whist keeping your hand as still as possible and carry the gun in a straight line (“pass”) across the work. The best way to obtain a smooth even pattern is to begin spraying about 6 inches before the work and 6 inches after the work and then release the trigger. After a few passes this will become second nature and the small amount of material lost will be insignificant. 

Before you begin to spray adjust the gun to the widest fan as possible to reduce the amount of passes needed to complete the work. The gun should be held approximately 6 to 8 inches away from the work. When spraying smaller pieces reduce the size of the fan and spray slightly closer to the work. You will quickly ascertain the correct size of fan and the distance to hold the gun for each piece of work. It is important to move the gun at the same speed as a brush stroke, however if the material is going on too light or too heavy then you must increase or decrease the speed of the pass. A pass should overlap the previous pass by approximately 50% or 100% if the previous pass is a light tack coat. A pass should also follow the same direction as the previous one to avoid criss-crossing as this can result in uneven coverage.


Organising the Work

Although the order in which the parts of a piece is work will depend on the size and shape it is important to always try and spray with the gun moving away from the body and towards the exhaust system such as open garage door, repellent fan, exhaust fan or when spraying outdoors into the direction of the wind. Before spraying it is good practice to make a dry run of the entire process. Start with the least visible areas and work towards the parts that will be seen. This will create an even finish and allow you to work around spots that may already have been covered. For instance when spray tabletops or kitchen cupboards it is important that the edges are sprayed first. In tight areas such as draws more wrist action is required and in some cases “feathering” or spraying lightly is required. When you become more familiar with the equipment you will develop a feel for how the gun responds and become more adept at controlling where and how heavily the finish is applied.


Cleaning Up

cleaning up It is essential that the entire spray gun is cleaned thoroughly after each project and when changing the type of material being sprayed. Always use the same material that the paint was thinned with to clean the gun, e.g. water, mineral spirits, etc. The most common problem is a blocked spray gun caused by dried paint being present in the tip, nozzle or siphon tube. Remember, when painting conventionally a brush that is not cleaned correctly results in unnecessary work when used again or in some cases having to be discarded.

After completing the project the compressed air supply should be turned off at both the regulator and pressure switch. Point the gun into an empty container and release any remaining compressed air that is present in the hose. Remove the cup/pot carefully and empty any remaining liquid into a suitable container; the gun can be put to one side for the moment. The pot should then be cleaned thoroughly with the appropriate solvents. Remember any paint that remains will dry quickly and be much more difficult to remove later.

Once the pot is completely paint free pour in a small amount of solvent and return it back to the gun. Any lids or gaskets should also be cleaned before sealing the pot back onto the spray gun. The nozzle assembly can also be cleaned at this stage.

When the gun has been re-assembled and attached to the hose, turn on the compressor and release the compressed air. Direct the gun towards an empty container and spray the solvent through the gun. For a few seconds the solvent will emerge with the material that was previously sprayed, however, this will quickly disappear and pure solvent will be present. The spray gun is now completely paint free and can be stored away. Please remember to remove the solvent from the pot using the same method as removing the paint.


Troubleshooting

Regardless of how skilful you are you are bound to experience some problems while spraying. The most likely are faulty equipment, your technique, preparation of the material or in some cases the weather. The chart lists the problems you are likely to encounter with spray painting.


Problem Cause Solution
     
Leaky packing nut Nut too loose Tighten packing nut
  Nut is worn or too dry Lubricate or replace nut

Air escaping from front of gun (non bleed) Air valve in trigger is stuck, worn or misaligned Clean and lubricate the stem or replace the valve, stem, spring or gasket

Fluid leaking from front of gun Packing nut is too tight Loosen nut
  Packing is worn or dry Lubricate or replace
  Fluid needle spring is missing or broken Replace fluid needle spring
  Dried finish or dirt in fluid tip Clean fluid tip
  Needle and tip are mismatched Replace with correct combination
  Fluid tip and/or needle are damaged Replace with new parts
  Fluid tip is loose Tighten fluid tip

Fluid leaking from cup Dirty or worn gaskets Clean or replace gaskets
  Cup and/or lid are damaged Replace with new parts