Sunday, 5 July 2015

Bracing the back and finish experiments

I am writing this blog post from a breezy patio covered in enough Jasmine blossom to look like snow. It's hubby's night to cook and I have a glass of something cold.... Ahhhhh.... Happy GBG!

This week I have completed bracing the mahogany back of the instrument. Now I need to do some cleaning up and then stain the outside of the back.


M has ordered a black guitar and this has prompted much experimentation with stains and finishes. I have pretty much decided on the Colour Tone range by StewMac.


The black is a lovely rich and deep colour that doesn't look grey when applied to a light wood such as spruce. There are two problems however: 1. It doesn't sink very deeply into the wood and 2. It's water based. I have to install the pale wood and malachite rosette after staining as otherwise the black stain will colour the pale wood lines. The rosette needs to be installed proud of the surface and then scraped back to flush. Any scraping of the surrounding black stained wood removes the stained surface. I've practiced a few methods and found that routing the rosette timber back to flush is more precise. I have now received the malachite and will test to see that grinding this back to flush will also work. The other problem is that the final polishing of the malachite is done with very fine wet and dry paper, wet! That's obviously not a great idea if the stain is water based. So, the stain must be sealed before the rosette is installed. For that and for the final finishing I will use a WudTone product. I used their range on my first guitar and it gives a nice finish and is simple to apply.

Here is the beautifully cut malachite from Small Wonder Music. This week I will be doing a trial inlay with this before I start work on the fox design.


That's all for now folks!

6 comments:

  1. What qualities does mahogany have as a sounding board? And does the stain/seal affect the sound to any extent?

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  2. Mahogany has a warmer more mellow tone than rosewood, which is arguably the most popular choice for the back and sides of an instrument. It is also somewhat easier to work with than the oily/resinous rosewood. This is particularly true when it comes to applying a finish. Mahogany takes a finish quite quickly whereas on rosewood the finish can take weeks to cure properly and will require more coats with large amounts of time in between.
    Any stain or finish should be minimal on a guitar. A little as possible to protect the wood and enhance the grain. You can't just use your average polyurethane varnish and expect a good sound. The timber needs to be able to resonate and breathe. In commercial factories an acid-catalyst finish is a popular choice. This requires specialist spraying and breathing equipment though and is not suited to a small home based workshop. Wudtone's finishes are very versatile. I clumsily dinged my first guitar before it was completed and I was able to sand out the mark and refinish just that small section and there is absolutely no perceivable join in the finish. Had it been a spray finish I would likely have had to strip it back and start again.

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  3. I hope the black is not too much a pain. Looks fab and terrifying!! Thank you. M

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    1. No prob Mark, the customer is always right! ;) It's going to look great.

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  4. Fascinating to see things progress, Amy - well done indeed! Cheers, Jonny.

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    1. Thanks Jonny, great to hear from you.

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