Luna: Ancient instrument in an exquisite case of unknown origins

Sona’s Etwahl is the biggest prop I have worked on so far, however that did not stop me jumping in to the deep end with it. I love the origins and background of the instrument and the fact, it floats.

I have yet to finish the Etwahl in fact I have a long way to go however here is a bit of a progress blog with some explanations for people as I have been asked several times by people about expanding foam, its uses, how to use it, what it does, and what’s the best.

I can not say that one brand is better than the other my attitude towards it is “expanding foam is expanding foam” as long as it is a new can and you shake it well before you use it you will be fine. The other contributing factor to make sure the foam expands properly is it needs to be warm! I usually do mine in a green house on a nice sunny day, 10 degrees+ is usually the best was to go, although too hot and it will just set right away before it has time to expand, so if you’re doping it in the middle of the summer its best to wait until the cooler mornings or evenings before you do it.


  • New Can
  • Any Brand
  • Warm temperatures
  • Shake the can well
  • Make sure the can isn’t stone cold (Please note the flammable warnings on side of can)

To start off with the main thing is know what prop you are making, you will then need to make a cardboard base for this like I had, this will be the base for your foam, as when it comes out of the can, it’s more like hair mousse. when I made my staff the base consisted of cereal box card and a simple basic twisted spiral almost, this was enough to put the foam onto, I done the same again for the Ring for my Aion Spiritmaster cosplay. Here is the base progress for the Etwahl

As you can see its just plain corrugated card, Cut and put together almost like a jigsaw to create the basic shape (and some added support on the inside to save on foam as it can be expensive). Then comes the fun part waiting for a nice day to go out and cover it in foam! Remember to follow the instructions, wear scruffy clothes as if you get any on your clothes there is no getting it off (this also means doing it out in the garden)! Make sure you also use the gloves provided which are usually on the inside lid once you have your stylish gloves on shake the can up for about 1-2 minutes. take the nozzle and hold it in your hand pointing away from you or towards your project screw the can into the nozzle. Do it this way around as sometimes foam can go everywhere without you doing anything (especially if it is your first time). turn the can upside down so the nozzle is at the bottom, aim FIRE! Remember to push pretty hard on the trigger, if you don’t  the foam wont expand as much, I learnt this one from experience.

You can only spray one side at a time due to the mouse like texture, it will roll off if you don’t Thankfully something like the Etwahl uses up a whole can for such a small area, on the image below I’ve only used 1 can, it goes a fair way. What if you don’t use the whole can? no worries leave the nozzle on. until you are ready to do the next bit, when you are just simply trim the end of the nozzle, and its usable again, just remember to be pointing it at your project before you continue.

Once you have done, leave to dry, this can take up to 1 hour to 24 hours depending on the foam, I suggest the pencil poke test to find out.

Below is the Etwahl after 2 cans, this will probably need another 1 or 2 before it is completely covered how I would like. As you can tell though in some places it has expanded more than others, this is due to where the sun was shining and how hard I was pressing on the nozzle.


  • Read Safety Instructions
  • Use the Gloves provided
  • Wear Old clothes
  • Do it outside
  • Make a base for the foam
  • Point the Nozzle at your project when putting it on the can.
  • Hold the Can upside down when spraying the foam
  • Apply heavy pressure to the trigger.
  • Spray one side at a time
  • Trim Nozzle if you’ve only used half a can to keep using.

“once it’s dry now what do I do?” Well first off Cover your floor or where ever you are going to do this, Newspaper or a bin liner is suggested! then take out an extendable craft knife and trim away any foam you don’t want starting with large chunks and then the details, work your way inwards until you have what you are looking for.

See what I mean about putting something down first? it takes ages to hover and pick it all up!

If you have holes it is up to you how you deal with it. Usually if I have a few holes, I take some off cuts glue them and cut it back again to the desired effect. If I have big holes, I grab another can of foam

Once you’ve finished carving it is upto you how you cover it, paper mache, followed by paper clay is a popular one, then sanding before painting, or worbla or wonderflex followed by gesso and sand then paint, the choices are endless. Below is My Aion Progress from last year, I even added in LED’s! The foam is perfect for making a straight cut into then pushing in wires to conceal them, or even concealing LED’s themselves! A word of warning Cover up the foam asap. Foam can go brittle in the sunlight after a week or so, you will notice it going a dark yellow, papier mache stops this easy enough.

Some of my projects i have used a glear gloss just to seal it all off (the spray kind for cars matt or gloss or the tinned furniture gloss), this makes it water proof which is great at conventions when itis likely to pour it down with rain.


  • Extendable craft knives
  • Warning mess!
  • fill in holes with off cuts or more foam
  • Foam goes brittle when exposed to long periods of sunlight
  • Completely cover in a favoured method
  • Sand
  • paint
  • Seal

I really hope this has helped you understand how I used expanding foam, and how I’m getting on with my Sona Etwahl, I hope you enjoyed this mini progress tutorial! Heres a few pics below to where it is now! it still needs more foam and more EL wire but hopefully be ready to cover soon and then I will break out another tutorial like blog.


One thought on “Luna: Ancient instrument in an exquisite case of unknown origins

  1. Very useful, just starting a male Sona cosplay and this should save me a lot of time figuring stuff out myself.

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