Guitar FX - Finishing Your FX Project Boxes.

In this instructable the DoomMeister will show you how can finish your project boxes for FX units in a professional looking way. These instructions can of course be used for finishing any type of project box.

The circuit that this particular box is intended to house is the Dr Quack an envelope filter which is a modified version of the Dr Q unit by Elecro Harmonix. A schematic can be found
here here more info here.

Step 1: You Will Need.

Drilled case, typically for a stomp box this will be of the die-cast aluminium type as manufactured by Hammond or Eddystone. You will have drilled this to fit your FX unit circuit.
Spay paints, acrylic or cellulose.
Clear lacquer compatible with the paint you are using.
Well ventilated space.
Face mask with correct filters.
Abrasive paper, wet and dry or glass paper. 250/300 grit and 1200 or above grit.
Water slide transfer paper, either ink jet or laser print. This can be found on-line or in a craft store.
Scalpel or razor blade.

Step 2: Preparation.

If you have access to a spray booth use that, otherwise find a well ventilated space, if its a living space or not well ventilated don't even bother starting this stage of the project. Lay down some newspaper as a protective covering, you do not want to spay everything in the vicinity lime green (or other putrid colour).

Make sure you have to hand a proper face mask or respirator with the correct filters for the type of paint you are using. Furthermore make sure the filter have not exceeded their working life. The DoomMeister does not care if you smoke 60 woodbine a day or want to get high off the fumes, you do not want to paint the inside of your lungs.

Before begining to paint the case the proper steps should be taken to get the paint to adhere and the finish smooth. In the case of a aluminium project box this means sanding the outer with 300 grit glass paper to not only remove any rough spots and scratches but to remove the oxidised layer of aluminium from the surface.

Step 3: Primer

Always choose the most appropriate type of primer for the material of your project box, in the case of aluminium this is probably etch primer due to aluminium having very poor adhesion properties.

Always choose the colour of your primer so that you can see how well your paint coat is proceeding and highlight any missing patches. The DoomMeister prefers grey primer because it works well with both light and dark colours.

When using small hand-held aerosol cans it is important to make sure that the can is properly shaken before use.

Spay the project box from a distance of around 12 to 18 inches using light horizontal strokes. It is preferable to use several thin layers than one thick layer.
If the paint is sprayed to thickly then runs will occur and the finish will need to be sanded back before the next layer can be added.

Step 4: Paint

When the primer is fully dry the paint layers can be added. If the primer is not smooth or has run then sand down the primer layer with 600 grit or finer wet and dry paper. If the finish requires sanding wash the project box under running cold water to remove the grit form the sand paper and leave to dry.

Again make sure that the paint can is well shaken. Spray in horizontal strokes making sure to keep the layer of paint a consistent thickness, you will achieve a much better finish by applying three of four thin layers than one thick one.

If the paint coat is not smooth or has runs you can carefully sand it down at this stage with fine wet and dry 800 grit or higher, finish with 1200 grit.

You don't have to just use one colour, the effect to can achieve at this point are limited only by imagination.

Step 5: Decals.

There are several ways of adding decals such as screen printing or clear sticky labels however the best way in the DoomMeister's opinion is to print your own onto water slide transfer paper. This transfer paper is available for either ink-jet or laser printers but the principle of use is the same.

Design your own labels and decals using a photo editing package such as Gimp or Photoshop, when you are happy with the designs print them out onto the special paper and let the ink dry. When the ink is dry then spay the labels with a thin layer of clear lacquer.

Cut the labels with a scapel so that there is perhaps a millimetre of white space around the edge. Now arrange the labels on the painted box dry so that you can see where best to put the decals.

When you are ready to apply the decals put the cut decal into a jar of warm water for around one minute. Try and float the decal on the surface of the water as this will save you having to go spear fishing with your scalpel. Now remove the decal from the water and position it above the box, carefully begin to slide the decal from the backing between thumb and fore finger. When the decal has begun to slide from the backing use a soft cloth or piece of kitchen roll to gently smooth it into position. When the decal is fully clear of the backing slide it in to the correct position and gentle start to press it down with the kitchen roll.

Leave to dry and repeat.
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Top Tip 1: If you are using an ink-jet printer you may find the that the decals are a little transparent especially on the blacks. If this is the case then double print the decals, let the ink dry and then re print the decals on the same sheet. Occasionally the paper may not centre correctly so take care to set the guides on your printer so that the paper cannot move.

Top Tip 2: Print as many decals as you can on the sheet leaving as little as possible white space, this way you get the best use out of your paper without having to pass small sections through the printer. Also print two copies of each set of decals as if you make a mistake (and it will happen) you do not have to start the process again.

Step 6: Clear Coat.

When the decals are dry it is now time apply a top coat of clear lacquer. Apply this in the same way that you spayed the colour and primer layers. Thin horizontal coats should be applied and once again several thin coats are preferable to one thick one.

When the clear coat is complete you should have fairly neat looking box, it it best not start assembling the electronics to the box for a least a couple of days in order for the lacquer to dry completely.

Last Thoughts.

To get the best finish proper preparation and patience are absolutely essential. It goes with out saying that you should always wait for the paint to dry before touching the project box as nothing will make you swear quite as bad as leaving finger prints in your nice finish. Also you working area should be as dust free as possible especially during the clear coat as retained dust on the finish will be especially visible.