Solar extractor with sterilised frames, old cappings and a beautiful cake of wax. Time to throw the cappings in the compost and replace the filter with a clean one.

In 2004 I built a solar wax extractor. The design was based on what I could find on the internet at the time, for example the ‘encyclopaedia Cushmanica‘ and good advice from beekeeping friends, both in Dublin and on the Irish beekeeping discussion group.  Here, eight years on, is what I have learned about building and using one.  Disclaimer: hot wax can burn, and wax is highly flammable.  DIY is not without risks.  Do all of this at your own risk!

Planning

Before you start, it is good to think about how you will use your solar wax extractor.  Will it stay in the same place year round or will it need to be moved to make space or stored away for winter?  How many hives do you have?  How often will you visit the extractor?  I have found that my extractor, which I keep in our back garden in Dublin, is sufficient for my needs, with 8 honeybee colonies. Over a good summer I’ve easily processed every frame I’ve found an excuse to put in it, plus my backlog, plus all the old combs of a friend.

If the spring/summer/autumn climate was warmer or sunnier, or if I did not go to work five days a week, I could process a lot more wax though this extractor.  If the extract was at an out-apiary and I only visited it when I saw my bees, throughput would be much less.

The solar wax extractor does two tasks for me:

• It renders used beeswax into handy cakes.  These I exchange for fresh foundation from Ben Harden, or I store for the day when I get into candlemaking.  The cakes of wax are not fully clean, as will be explained.
• It partially cleans cleans and (when the temperature gets properly hot) sterilises frames.

Moreover it is most satisfying that all the energy costs come from the sun!

Construction

Casement window – starting point for my solar extractor

To build this solar extractor I started with a double-glazed hardwood casement window in its frame, donated by a friend. The basic idea is:

• A double-skinned box, made of plywood with fibreglass insulation between the inner and outer box.  The inner box was built off the inside of the window frame.
• 
• The outer box is made of marine ply, and is built off the outside of the casement.  Fibregless and bubble foil insulation were put in the space between the two boxes.
  

  Outer box face down, showing insulation, awaiting back cover

• The inner box is shaped to hold an aluminium tray.  Along the bottom edge of the tray is a notch for the wax to drip out through.  Below the tray is a space where the the receptacle that catches the molten wax goes.
• In the aluminium tray goes a removable mesh tray (made from expanded metal), raised slightly up off the tray floor with short bolts.
  

  Inner mesh tray with old cocoons ready for the compost. Note t-shirt filter.

• Fixed around the inside of the the mesh tray is a cloth filter (usually an old t-shirt, cut in half up the sides and across the shoulders) in which I deposit the wax.
• The whole assembly is painted black to maximise absorption and is mounted on four legs, two of which have wheels.  The original white wheels shown in a picture further up proved unsuitable for the weight of the extractor on the terrain, so I used these larger black ones (from a gas barbecue that my brother-in-law had helpfully abandoned in our garden) instead.

Using the solar extractor

Here are a few notes & things that work well:

Washed cappings awaiting melting, in a new t-shirt filter.

1. It processes cappings (they tend to get a fresh t-shirt filter), brace & burr comb, super comb and brood comb.  I like to wash cappings first to remove most of the honey.
2. You will see an oven thermometer belonging to my brother’s ex-wife. That works well, but the extractor doesn’t really need one.  I’ve recorded temperatures up to 120C (therefore anything in or near the heating area needs to be heat-proof, and you need to keep children away on sunny days).
3. I chose the angle of the tray by looking up on the internet the correct angle for solar water heaters.
4. Almost all solid impurities are filtered out by the cloth filter – and the wax seems to flow down in 2 ways – down the front of the cloth to the bottom where it passes thru the cloth at the bottom, and straight thru the cloth & the mesh and then down the alu tray behind. Once the cloth filter gets dirty I replace it and use the old one (with most of the wax melted out of it) as a firelighter in the stove.  This works well for me.
5. I try to remove frames while they are still warm (but not too hot, ideally) because the residue sets solid when cold.  I use the knife to scrape the worst of any adhering cocoons or propolis off them, then they’re ready for more foundation.  Gloves are good because the residue can be a) hot & b) very sticky.  Manky brood frames then get cleaned sterilised in caustic soda & boiling water.
6. The cocoons that are left after melting old brood combs go onto the compost, once I’ve removed the wires.
7. Every autumn the extractor gets put away at the bottom of the garden with a plastic sheet over it.  When the extractor gets wheeled back up and put on the deck it’s a sign in our house that spring is here.  The extractor is scrubbed and cleaned with boiling water before use.
8. I made the inner tray wide and long enough to fit a queen excluder in, on the advice of my friend Joe Kelly.  However, I’m not too happy about the effects on the wooden joints of the metal expanding in the heat, so I tend not to use it for queen excluders.  Still, it’s useful to have a big extractor – useful for cleaning my travelling screen and so on.
9. I collect the wax in old pyrex dishes or pots with a few mm of water in.  The idea of the water is to dissolve the honey out of the wax, but the collection pot rarely seems to get hot enough for the wax to be liquid by the time it arrives down there.  Pyrex dishes are used instead of the bread tin that you see in the picture because they don’t rust.  I get the wax out by pouring hot water on the underneath of the dish, or by putting the dish in the freezer.  My pyrex dishes come from the charity shops or the bric a brac stand at my local church fair, not from our kitchen!
10. Having the door is hinged at the side seems to be right.  It may want a string or a prop to hold it open.
11. As you will see in the top picture, I keep an old knife in the collection area for prising stuff out and cleaning frames.
12. The extractor works on sunny days from about April to October.  I keep others’ wax separate because of disease & so I know whose pot of wax is whose.
13. With my solar extractor, the solid impurities are nearly all removed by the t-shirt filter but one ends up with residues of honey left in the wax. This means I need to process the wax a second time to wash out the impurities.

I should point out that many of the smarter ideas come from other beekeepers (thanks all).

The extractor has done its work – the wax has melted and run trough the filter, from the tray and into the pot below. Note the residue left on the t-shirt filter. Either side of the pot that received the wax are two more that I made earlier.

Improving this design

The above is by no means a perfect design for a solar extractor.  Here’s what I would do differently if I were to do it again:

1. Does it really need a double-skinned box?  I think so, but I’m not sure.  It probably keeps the temperature up on sunny/cloudy days.
2. 

   Alu tray with notch for wax to drip into receptacle below

   The lip at the bottom of the inner tray is horizontal. It would be better to have a slight gradient from the sides to the centre, by shaping the lip into a slight V.

3. I’d put the wheels on a proper axle.  Just mounting each wheel on a bolt is probably not strong enough.
4. I’d fit a handle for pulling it round the garden, or even fit it into an old wheelbarrow chassis.
5. I’d try to make a box that wasn’t as deep.  It’s very bulky (which means heavy) & it doesn’t need to be that big.
6. When it rains (it does that a lot round here), water can get in thru the window seals and into the inner box.  I added a lip on the window just above the top of the door and I built up the botton of the window with silicone sealant, which seems to have done the trick.  Perhaps a better design might be to get a double-glazed window pane, not in a frame, that is bigger than the box and lies on top of the box so there are no seals/joints at the front.  The rain getting in has meant that some of the marine ply has got rotten.  I wish I’d put extra effort into weatherproofing it, but perhaps it goes with the territory.
7. The fibreglass in the space between the inner & outer boxes is probably fairly superfluous – it doesn’t seem to get hot enough down there to really matter much.
8. Oh, and I’d move to live somewhere sunnier.
9. One problem with this design seems to be that the wax needs to be liquid to pass thru the t-shirt filter, and the top of the extractor seems to get a lot hotter than the bottom, so it can get discoloured by heat before it makes it into the tray.  One day I may experiment with leaving out the t-shirt and collecting wax with solid impurities in it, to see if that improves the overall colour of the wax.  I think if I made the bottom edge of the alu / mesh trays about 50-75mm higher up the box and made the inner box smaller, this might make it it warmer down below and possibly solve the problem.
10. I’ve been musing on the idea of a wall-mounted extractor.  It would swivel on gate hinges, and be angled much more to the vertical.  It would need to be smaller, but might be more suitable for a smaller garden.  Perhaos it would tuck away when not in use.

My next challenge is to get the honey residue out of the wax cakes, then someday I might make candles.  When I do that, I might use the solar extractor as a third stage to re-filter the wax thru gauze to take out the final few impurities.

Edit: Feedback received

In addition to comments below, I’ve had some feedback orally and by email.  Here are some of the points:

• At least one beekeeper in Ireland has had success with a single-skinned box and single-glazed glass. I’m coming round to the idea that a single skin is adequate.  It would be interesting to test the 2 extractors side-by-side
• Here is a different extractor design – a single-skinned bof with insulation inside.  Thanks David!
• One beekeeper mounted his solar extractor on an old swivel chair. It must have been a smaler & lighter extractor design than mine, but it sounds ideal for flat ground.
• Another beekeeper recommends using a lid of corotherm polycarbonate.  I’ve no idea what heat the polycarbonate will support, but he reports that his works well.
• There has been a good discussion based on this post, in the ‘Beekeeping worldwide’ group on Linkedin.  One contributor uses a metal barrel cut in half, and another suggested these plans for a solar wax extractor.