Didgeridoo Design, Make and Play
Seal the bore to protect and preserve the wood.
Some people will argue that you don't need to seal the bore of your didge, others would argue the opposite. It comes down to personal taste and preference. The bore does not have to be sealed, however, by doing so the life of the instrument can be prolonged and the quality and clarity of the sound improved and retained.
Before sanding the outside I seal the bore. I do it at this stage for several reasons. Firstly, the sound may alter, whether in tone or in pitch. If it changes the sound too much I have the opportunity to adjust the mouthpiece or bell accordingly. Using Danish oil as I do to seal the bore, I found that it leaks through any holes in the wood I was not previously aware of, or knots that have not been completely sealed. Sometimes the holes are so small, that several coats of Danish oil will fill them without the need of further action. Needless to say this will also have an impact on the sound of the didgeridoo.
I have experimented with several substances for sealing the bore's in didgeridoos that I have both bought and made. I have tried to weigh up cost, ease of use, toxicity, availability, longevity and importantly, effectiveness. Some people do not like anything to coat the inside of their didgeridoos on the basis that it detracts from the natural sound of the wood.
I have written some notes on different materials used below. I prefer to use Danish Oil and this is how I apply it. For a more detailed description with loads of phots, visit Didgeridoo Maintenence - Re-Sealing the Bore.
I close off the mouthpiece end of the didge with a small ball of plasticine pressed into the wood. I leave a portion of it sticking out so that when turned upside down, the wood is protected. If pressed in the end firmly, the plasticine creates a good seal. Then with the didgeridoo upturned, I pour in the Danish oil. I have a rag to hand that I squeeze into a tight ball, and place into and over the bell to prevent leakage.
Placing a gloved hand over the rag or cloth in the bell and applying pressure to create a good seal, I lift and rotate the didgeridoo up and down, and round and round, listening to hear the liquid flow in all parts of the bore. When I am happy this is done, with the didgeridoo upside down, I remove the rag or cloth from the bell.
Carefully and slowly, I turn the didgeridoo the right side up with an old plastic jug to catch the excess oil. After letting it drain into the jug for a minute or so (until the drip becomes less frequent), I place the didgeridoo over a wire rack in a washing up bowl and allow it to drain for 5-10 minutes (allowing me to attend to the plasticine).
Gently removing the plasticine with a rag I wipe the inside of the mouthpiece. This ensures the mouthpiece has a good coating of the oil and any small crumbs of plasticine left on the wood can be wiped away. The plasticine is put to one side, to be used again, and the didgeridoo is placed on a stand to fully dry.
With all my didgeridoos, I coat the bore at least four times to ensure there is a good protective layer that will last for some time. When the need arises for recoating the bore I use the same process but only apply 2 coats. The oil is thin and I have not noticed a build up of layers that detrimentally affects the sound, as can happen with a number of other substances.
There is no doubt in my mind that natural wood has a particular sound. However, I think of a didgeridoo that has not been treated internally, and surmise that the surface of the bore has, over time, and frequent changed from that of natural wood to a coating from the moisture accumulated. The older and more frequent played instruments this build up will be greater. Imagine the mouthpiece without ever cleaning it, or having beeswax that is never replaced or cleaned, then think of the inside of a didgeridoo.
I do not think that sealing the bore is a bad thing so long as whatever is used retains the natural feel.
This is my preferred substance for sealing the wood of a didgeridoo. I use it internally as well as externally and also with other wooden items I make. It provides a protective coating that soaks into the wood and sets hard. By soaking into the wood the natural sound is retained. It is readily available at DIY stores, ironmongers and hardware shops. The oil sets hard, as I've said, and does not react with skin when cured. Designed for use in side and outside it has good resistance to moisture. The liquid is brown in colour and will give a nice depth to pale coloured wood.
A couple of downsides to Danish oil, firstly the liquid is flammable and needs to be disposed of correctly. Spontaneous combustion can occur if rag or cloth is not given sufficient room to air and dry, and secondly, allow a lot more time than it says on the tin when drying the bore. With 3 to 4 coats of oil (depending on brand of oil) I will not do anything more for at least 1-2 weeks. If it is not fully dry, it leaves an after taste when playing which is not nice!
Boiled Linseed Oil
Boiled linseed oil is most commonly associated with cricket as it used to oil the cricket bats. I used it on recommendation on the first didgeridoo I bought. It has a strong odour, and does not dry as a hard layer, but remains wet. Although I like the smell the oil gives off, I found it awkward to work with. It is thinned with methylated spirits, and takes some time to dry enough to be able to play the didgeridoo. However it does the job well of protecting the wood and appears to last. Make sure, if you use this substance that you buy boiled linseed oil as the other variety (un-boiled) can affect the skin. Widely available in ironmongers, hardware, as well as DIY shops, and many sports shops.
Epoxy resin, as I have written elsewhere on these pages, is a two part compound that when mixed together, reacts and sets into a solid hard mass. It is durable and resistant to many chemicals, has a high surface tension leaving a very smooth shiny finish. Materials can be added to make it thicker as can colour also be added. I use epoxy resin for many purposes in making my didgeridoos but not for sealing the bore.
It does everything it says on the tin, however I feel the sound does not sound truly natural. As it creates its own layer and the sound bounces of that, a lot of the resonance in the wood is lost. It still sounds good, but why use wood in the first place and why not make a didge completely out of resin. Due to the resin being toxic and a skin irritant prior to curing, and having had some resin fail to set on me (which took forever to clean up) I am not willing to use it on parts of the didgeridoo I can not reach, though the resin can be applied before gluing. Different viscosity resins can be purchased (invariably) with a longer working and curing time, the layer tends to be thick compared to other finishes such as the oils mentioned above that can significantly narrow the bore and change the sound.
Because the cured resin does provide a totally waterproof barrier, it can be washed and cleaned very easily, without the worry of causing any damage. You will not have to reseal the bore. I know of several didgeridoo makers that use epoxy resin and the didgeridoos in question are fabulous instruments, it is just not my preferred method.
PVA (Poly Vinyl Acetate) is versatile and readily available, is waterproof (if you buy the right variety), is non toxic, and cheap. It can be thinned and used to seal bores in didgeridoos quite effectively. It dries clear from being white when wet. I have several didgeridoos both bought and made that have been treated with a dose of PVVA in the bore. The sound crispened up somewhat but has not otherwise changed it. Each didge had 3-4 layers applied. The first one being a 1:1 ratio mix, the remainder being a thinner mix of approximately 10:1 ratio, both mixed with water. I do this so as not to impact the build up of layers inside the bore.
I have noticed a smell of something like vinegar when the didgeridoo has been played for a long time. PVA has many uses, and I no longer seal the bores in my didgeridoos anymore, more this main reason.