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Questions of the Week #1

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Welcome to our new weekly(ish!) blog post where we'll round up some of the more interesting and important questions we get asked about our products, techniques, future plans.. anything, really - if we think it might be of any interest to the wider community we'll publish our responses on the blog.  If you have any questions you'd like answered and featured here please email us on info@rkfst.co.uk, or us the contact form on our website.

1) I've read on forums that you need to spray metallic paints differently to solid colour paints, is this true?

Metallic paint should be built up in very fine mist coats. You don’t want it to ever look ‘wet’ when it’s sprayed, otherwise the metallic flakes will sink in and you’ll get dark patches (visible metallic flakes, which are small particles of aluminium, have the effect of lightening the colour, hence if they sink the paint looks darker in the area where they have sunk). Alternate the direction of each successive coat by 90 degrees. Then, the final two coats should be in the same direction. So you might do it like this, with — and | signifying the direction of spraying:

Coat 1: —

Coat 2: |

Coat 3: —

Coat 4: |

Coat 5: —

Coat 6: —

2) How do I apply a clear coat of lacquer over metallic cellulose paint?

Cellulose paints and nitrocellulose lacquers are solvent evaporation type finishes. They dry because the solvent evaporates and leaves behind the resin of the finish. No chemical change occurs in the resin itself. As a result, if you apply more of the solvent it will re-dissolve the resin. This is how layers of nitrocellulose lacquer burn into one another, so if you spray multiple coats you end up with one thicker coat. If you spray multiple coats of a catalysed lacquer you end up with lots of separate layers, like an onion.

The effect of this when you are spraying metallic paints is that you need to spray the first coats of clear lacquer very very lightly, so very little solvent lands on the surface. If you spray a wet coat of clear lacquer over a metallic the solvents will re-dissolve the resins in the metallic paint causing the metallic flakes to sink, and you will lose the metallic effect that you worked so hard to achieve in the first place.

3) Will your waterslide decals stick to perspex?  I need to do a logo underneath a pickguard.

Yes!  Waterslide decals will stick to almost any surface which is non-porous, smooth, and not oily or greasy.  This includes metal, painted metal, perspex, plastics and lacquered wood.  The main consideration is that usually the decal needs to be lacquered over for protection, so you need to make sure that whatever material you are putting the decal on to can take whatever lacquer you plan on using to seal the decal.

The most common reason for applying decals to perspex in the guitar world is when making custom pickguards or truss rod covers where a logo is visible through the clear perspex piece, with the perspex then painted a solid or metallic colour on the back.  A great example of this is the long truss rod covers seen on Rickenbacker guitars.  To recreate this effect you need to first cut your perspex to the desired shape, then apply the waterslide decal to the back, and then lacquer or paint over the back of the perspex to finish the effect.  Of course, for the text or logo to look correct from the top once the trc or pickguard is fitted the decal design needs to be mirrored before printing, something we an easily do for you.  If you'd like to try such a project and need a decal for it please don't hesitate to get in touch.

4) I want to paint a gloss black finish on my Les Paul headstock but don't have the space or equipment to use cellulose paints.  Can you recommend an alternative?

Cellulose paints give a great finish, the pigments we can use in them offer excellent opacity and depth of colour.  However, they're not for everyone - to use them you need an extractor with a carbon filter, a suitable facemask, goggles, nitrile gloves, overalls, and somewhere to spray where the solvents won't affect anyone nearby.  Because of this we have developed a new range of waterborne paints as an alternative for the home luthier and hobbyist.

Our new black waterborne paint is ideal for your headstock, easy to apply and free of the fumes associated with cellulose finishes.  Once applied and polished it gives a lovely thin finish and should be almost indistinguishable from its cellulose counterpart.  Check our our Waterborne Paint category for our ever growing range of colours:  http://www.rothkoandfrost.com/waterborne-paints/

Cheerio,

Simon

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