DIY Tea-bubbler

[neongreen]

Hi all,

Most people just use a bucket, some kind of porous bag container to hold their tea mix, and a powerful air pump to aerate the brew, but I've decided on a slightly different approach since I think that I can improve on the traditional approach.

The trouble with using ordinary containers to hold your brew is that they are usually wide and shallow, which means that as a bubble rises through your tea, it only has a short time to give up it's oxygen. My bubbler in contrast is constructed from a 2.5 foot (73.5 cm) length of 4 inch (103.5 mm internal diameter) PVC pipe, so it's narrow and deep.

This is at least twice as deep as a bucket, so bubbles take twice as long to rise through the column as they would in a bucket, so in theory the same air pump should supply at least twice as much oxygen to the tea when used in this way. It means not having to spend so much on a powerful air pump, and also savings in electricity.

My design also ensures that the mix you use to brew your tea is very well aerated since it's held in place by a snuggly fitting "cage" and air is then forced through it. Forcing air through the cage and mix should also help to break larger bubbles up, increasing surface area, and therefore aeration.

There may still be a couple of minor bugs in this prototype which I hope to iron out later on, but the principal seems sound, so I'd like to share it with everyone, and a quick guide on how to build it.

A - Pipe Wall
B - MDF Base
C - Cage (screw-lid tub)
D - Screen (anti splatter screen)
E - Screen holders
F - Washer
G - Spring (coat hanger wire)
H - Air hoses
I - "Bubble curtain"
J - Air stones
K - Wax
L/M - Silicone


Here's what the bubbler looks like


The bubbler itself was pretty straightforward to construct, and quite cheap. I checked a few hardware/plumbing supply stores until I found one that would sell me a pipe of the right size. Luckily I found one that had an offcut that they sold me cheap.

For the base I used some MDF that was leftover from when I built my cab.

The bubbler can make one gallon (4 liters) of tea which should be enough for my needs, but I think the design is good for larger volumes if slightly larger diameter pipe can be found, and the pipe is well set into it's base. Any taller than this probably makes it harder to construct/use.


Here's what I did:

1. Clean and cut the pipe. It was a bit uneven when I got it, and although I didn't have to (this part is mostly cosmetic, unless your pipe is in really bad shape), I carefully marked the are to be cut by slowly rotating the pipe on the carpet, held in place by a wall along it's length, and prevented from moving around length ways by a jutting out piece of door-frame.

I then placed a sharp object against the pipe, using the floor to brace/keep from moving too much, and rotated the pipe, leaving it scored along the area I wanted to remove. I then used a hacksaw to saw off this section.

Since the plastic melts easily when you are cutting it, you can't saw too fast, and I've found it's good to use different parts of the blade, and alternate them when that part gets too hot and stops cutting efficiently.

Repeat if necessary for the other end, although if it's only ugly there is no need to to anything since one end will be unseen and embedded in the base.

I left the final finishing off (sanding down) till last, since it's easier to do with the base attached.

2. I used a roughly A4 sized piece of MDF for the base, but If you use a longer pipe, an appropriately larger sized base would be necessary for stability. The fist stage is to place the pipe in the center of the base, and mark it all the way around with a pencil. I did this by eye, but if you want to be sure the the pipe is dead center, a tape measure/ruler to check is a good idea.

For the next stage you'll need some more tools - a hammer, some fine chisels if you have them, and a sharp knife. I also used a calliper to score the surface.


Using the caliper I found the center of the circle, and marked that spot by gouging a small hole with the sharp end. Next we need to find the thickness of wall of the pipe (or just judge it by eye like I did) and adjust the caliper so that it scores a circle that is just inside the circle drawn previously, but not more than the thickness of the pipe wall, or the pipe won't fit snuggly.

Give the caliper a good few turns (10-15), then check that the groove you've just created is not too wide - the goal here is to create a circular groove that is narrower than the wall of your pipe. As you finish it off, you can widen or narrow it, to make it fit snugly.

Now go around the edges of the groove (both inside and out) with your knife a couple of times, being careful not to place your fingers where they will be cut if the knife slips.

Taking your time, work the groove deeper with the chisels and hammer, followed by more knife, and so on. Keep checking all the way through that you're not making it too wide or narrow.

After a while, you should have a smooth circular groove that's nearly half the depth of your base, and it should be just a tiny bit too tight to push the tube in.

Now you want to go really slow, just taking off little bits using knife/chisel as needed, till you get to the point where the pipe can be pushed all the way into the groove.

3.

The next step is to attach the pipe to the base and secure,make it watertight with some silicone sealant (the type used for/window frames, aquariums, kitchens, etc). First I filed the entire length of the groove with sealant, then I pumped out a big dollop (nearly half the tube) so that it spread outwards from the center, flowing out and over the groove. I then inserted the pipe into the groove, went around the join with a bit of semi-stiff card to give a convex (sloping down, and away from the base) join, rather than the concave natural join the would have formed if I'd left it at that, which would be prone to collecting any fluids. I also spread some more silicone around the base, and sides, although I have yet to seal the underside.



Let it dry for at least 24 hours now. I sped things up a bit by sticking a few air hoses down there after 3-4 hours to bring in fresh air and help it dry.

Optional step

4.
I finished off with some medium-course grain sand paper which I duct tapped on all sides to a flat surface.

I splashed a little bit of water from a cup I had beside me on the sand paper to keep the dust down, then stood the pipe up on the sandpaper and holding it low down, used a slow and consistent round and round motion to smooth away the edge. It's important not to be to fast, or the pipe won't move smoothly across the sandpaper. If it starts to oscillate, slow down and keep it steady. It can take a while.

Optional step

5. Since the sealant I used contained fungicide, which I only discovered after having performed steps 1-5 and then read the label (doh!), I decided to seal the sealant with a layer of candle wax, for which I melted down a pair of white paraffin wax candles in a small cooking pot, and poured down the tube using a tube of rolled up and sticky-taped newspaper that was long enough to reach to the bottom of the pipe, plus a funnel also shaped out of newspaper.

I roped a helper into holding the funnel and tube while I pored the wax. I made sure the tube was vertical and in contact with the bottom/base of the pipe before poring the wax in quite quickly, and immediately lifting the paper tube, otherwise the hot wax would fly down the tube and splash the inner walls of the pipe, instead of forming a pool at the bottom.

Once the wax is all out, the paper tube can be carefully lifted out. Leave to cool for about half an hour, and it's ready to use, however you're not done yet!

 

[neongreen]

The screen cage

The screen cage

The aim of my design is to force air through the tea mix, and to do this you need some kind of a container or cage that fits snuggly into the pipe. You'll also need some material that's porous enough to allow the flow of water/air/microbes through it whilst at the same time the gaps are tight enough to hold most of the larger particles and keep them from mixing with your tea, just like a tea-bag.

I went hunting, and came back with a "anti-splatter screen" for frying pans which has a fine metal mesh that has gaps I estimate to be somewhere around 0.5-0.75 mm wide, which is a little on the large side, but it should do the job. I also found a plastic tub containing a cosmetic product (the most expensive single item apart from my air pump) that had an outer diameter that would fit perfectly into the pipe. I also got a few weird looks whilst going round the cosmetic section measuring likely looking containers

It was worth it though, as the container fits almost too tight - I have to ram it (carefully) down into the pipe!




It might also work well using just a cage made from screen instead of a plastic screw-top container like I did, if you can fashion it into the right shape, and incorporate tubes which you can slide the air hose/air hoses down. It might even be easier to construct (this was fairly fiddly) and easier to find the right parts.

In my design I've got two air-hoses that pass through the cage, which each pumping air at the rate of up to 200 liters per hour, and a third attached to a "bubble curtain" inside the cage, although all of these may not be necessary if you have a more powerful pump or a pump with a single air outlet.

I think even my relatively small pump may be overkill using it this way, and I will try turning down the power, and see if there is much of a difference in the tea produced at some point.


Here's how I made it

1. After washing the tub out thoroughly, I marked out the areas I wanted to cut away from the tub, and used a Dremel on slow speed with a cutting head to make small straight cuts were my guidelines were not straight. I made sure that I was leaving a good sized lip at each end, but most of the base except for the lip and a small area to guide the air-hoses through, which serves no real purpose, and I may remove, since it stops the air-hoses that travel through the cage turning when I screw on the lid.



I finished off the cut edges with a sanding attachment on my Dremel, then drilled the holes in the remaining part of the base for the air hoses to pass through.

2. The next step was to make the screen holders and washers, which are both made out of the same material. I used the bases of 5 inch plant-pot saucers, which are made of fairly flexible/thin plastic.

I cut out the flat sections of the saucers using a pair of scissors, then marked off with a permanent marker where I needed to cut. For the inside cuts I used a knife, but it was easier to trim the outside edge to size with a sharp pair of scissors. Luckily for me, the saucers I used had a raised rim exactly at the diameter I had to cut, which made things easy since all I had to do was cut around it.



I messed up the holes pretty good on the holder above, so I cut a new one, and punched the holes (rather than tried to drill them) using a small piece of metal tubing that had the right diameter to fit snugly around the air-hoses.

In my design the upper and lower screen holders/washers are identical, except that the screen holder that fits in the lid has three holes in it for air-hoses instead of two.



The washers are just screen holders with the inside completely cut away to leave them perfectly round on the inside. These help to let things turn without catching when screwing the lid on.

3. Next you need to cover the screen holders with screen (duh!), so using the screen holders as a stencil, mark out on the screen where you want to cut - remember to mark out an area a bit larger than the holder itself, so you can wrap it around which will help keep it in place.




One trouble with this design is that there is a gap between the holder and the filter, and the best way I could think to close it off was to stitch it up using strands of copper wire taken from an electrical cord. I punctured it with holes made using a safety pin that I held between some cardboard. and made sure the ends were well tied off. I realized after that I should have stitched all the way to the sides for a perfect seal, but I think this will still work OK.



Watch out for all those small sections of metal screen wire that go everywhere when you cut it. I used a previously sharp pair of scissors to cut it to size, and found some stuck (magnetically) to those. I also recommend a magnet to sweep any area where you think they may have escaped to. It's better than having them wind up in your feet

Also, get stainless-steel screen, for obvious reasons. I have no idea if mine is stainless, but I should know in about 36 hours


4. The only thing remaining is to make a spring to keep the screen holder at the lower end of the cage in close contact with the lip of the container, otherwise there may be gaps and the screen will not be held properly in place. The screen holder that fits in the lid is held in place by the lid. I used wire from a coat hanger which I bent into shape using a pair of pliers. I made sure that any sharp ends were bent inwards/away from the plastic container as much as possible.



Now your cage can be assembled, filled with a mix and put to use







Sorry about the quality of some of the pics, but it's been a long weekend!


The whole project took me about 2 days including drying time to complete, and I hope to improve on the design in the future. I have also yet to see how well (or badly) it works. The first batch of tea is brewing as I type!

For my first 4L (1 gal approx) brew:

1/4 tsp blackstrap molasses
5ml (1/4 of a cap full of seaweed)

3 tbsp. farm manure
3 tbsp. soil from a nearby, and very old woodland
3 tbsp. compost/soil from garden
3 tbsp. castings
1/3 tbsp. bat guano

There was room for a bit more in the cage/container which was originally designed to hold 16 fluid ounces, but a slightly larger container might be better.

I'll be back when the tea is ready with a report. In the meantime I welcome any feedback, questions, or ideas.

ng

 

[Microbeman]

Looks like a lot of work. I think it will serve your needs. Does your pump actually output 200 LPM? This is enough for 70 gallons. I would not recommend this design for larger brewers, as the majority of gas exchange occurs at the water surface to atmosphere interface where CO2 is released. Dissolved O2 (DO2) in water is dependent on the release of CO2. In experiments we ran, we actually found shallower (within reason) wider shaped brewers more efficient at raising DO2 because of the increased surface area. Your theory does make sense, when applied to air lifts which return into the main tank so air lifts returning to a main tank, with open surface = good gas exchange = good DO2. At least that's my take.

 

[neongreen]

Hi Microbeman

Looks like a lot of work.

It looks more complex than it is I think, and yes, that is basically all I did for two days, so it is a fair bit of work. The cage design is a bit more fiddly than it could perhaps be, but I think that can potentially be done allot easier. I may try an alternative design like the one I suggested.

I think it will serve your needs.

I hope so. I only have a few plants, although they should get quite large (they will be outdoors), and I may have to dilute more if it's very dry/hot for a long period during summer.

Does your pump actually output 200 LPM?

My bad - it's actually 200 LPH (x 4)!

I would not recommend this design for larger brewers, as the majority of gas exchange occurs at the water surface to atmosphere interface where CO2 is released. Dissolved O2 (DO2) in water is dependent on the release of CO2. In experiments we ran, we actually found shallower (within reason) wider shaped brewers more efficient at raising DO2 because of the increased surface area. Your theory does make sense, when applied to air lifts which return into the main tank so air lifts returning to a main tank, with open surface = good gas exchange = good DO2. At least that's my take.

Interesting to hear your experience. Thanks for sharing. I think that the lack of surface area at the surface of the water will be more than made up for by the increased surface area by the bubbles produced. Gas exchange should occur both ways, whatever the surface.

I think that if you had used lots of aeration in your experiment, more of the CO2 would be released into the bubbles, so it would balance out more, like it should do in mine I hope.

Just curious, did you have a way to accurately measure DO2/DCO2?

I may have a look to see if I can find something, if it's not too expensive. I remember the kit that I used when I was working in a lab looked fairly expensive, but that was a couple of decades ago now. I also remember calibrating the probe was a nightmare!

Thank you for your input Microbeman.

 

[jaykush]

seems like it would be a bitch to clean. ive tossed multiple brewer designs in the trash for stupid reasons but its ok. all i can say is good luck, and do LOTS of testing. oh and brew a real compost tea with compost, loose the guano and the manure imo. keep it simple for now. too many variables means too many things to keep track of too many things to go wrong.

 

[Microbeman]

Yes I used DO2 meters and yes they need calibrating every use. I researched everything from a half gallon container with an aquarium pump up to a 1200 gallon tank with a 95 CFM air pump and 4 four inch diameter air lifts. Check out my page if you like;
www.microbeorganics.com

 

[neongreen]

seems like it would be a bitch to clean. ive tossed multiple brewer designs in the trash for stupid reasons but its ok. all i can say is good luck, and do LOTS of testing. oh and brew a real compost tea with compost, loose the guano and the manure imo. keep it simple for now. too many variables means too many things to keep track of too many things to go wrong.

Good points jaykush.

I hadn't considered the cleaning aspect. I can just reach the bottom, so with a brush there won't be too much of a problem, but I agree with you, it would certainly be more hastle to clean than an ordinary container.

Thanks for the tip on the tea. I wasn't sure which ingredients would be best to start with, but my main aim with this first tea is to inoculate my plot/surrounding area with as varied a selection of beneficial micro fauna as possible. The manure (which seems well composted and mixed in with other stuff like wood chips) and guano I thought would both be good sources too.

Can I ask which ingredients you'd recommend for a simple tea? The compost I have (kitchen waste/lawn clippings/etc) is still maturing (I turned it over a month or two back, mixing well composted (1 year) with relatively recent additions.

--

Quick update on the brew at the half way point - it's been bubbling away nicely, and a good head of froth is starting to develop. Seems to be working!

 

[neongreen]

Yes I used DO2 meters and yes they need calibrating every use. I researched everything from a half gallon container with an aquarium pump up to a 1200 gallon tank with a 95 CFM air pump and 4 four inch diameter air lifts. Check out my page if you like;
www.microbeorganics.com

Sounds like you did some pretty thorough testing!

Thanks for the link Microbeman. Lots of info by the looks of it. I'll bookmark it and study it later.

 

[jaykush]

I hadn't considered the cleaning aspect. I can just reach the bottom, so with a brush there won't be too much of a problem, but I agree with you, it would certainly be more hastle to clean than an ordinary container.

yea i had one brewer design bout a year ago, it worked great. accept it would get some anaerobic spots and just collect biofilm, and it was a bitch to clean properly. just a heads up of course.

Thanks for the tip on the tea. I wasn't sure which ingredients would be best to start with, but my main aim with this first tea is to inoculate my plot/surrounding area with as varied a selection of beneficial micro fauna as possible. The manure (which seems well composted and mixed in with other stuff like wood chips) and guano I thought would both be good sources too.

at the moment i would keep it simple, either use quality wormcastings or compost. you can add a tiny amount of guano as it does have some microbes but not as much as a good compost. maybe you can do a brew with each apply to different plants and take notes.

Can I ask which ingredients you'd recommend for a simple tea? The compost I have (kitchen waste/lawn clippings/etc) is still maturing (I turned it over a month or two back, mixing well composted (1 year) with relatively recent additions.

when im testing new designs, which im actually doin atm. im just using homemade compost, stream water from our property, and a tiny bit of molasses. i would not use unfinished compost. in your second post you mentioned castings, are they a good source? if so thats what i would use until the compost is finished.

 

[neongreen]

yea i had one brewer design bout a year ago, it worked great. accept it would get some anaerobic spots and just collect biofilm, and it was a bitch to clean properly. just a heads up of course.

That's exactly the kind of feedback I'm looking for. Thanks jaykush.

at the moment i would keep it simple, either use quality wormcastings or compost. you can add a tiny amount of guano as it does have some microbes but not as much as a good compost. maybe you can do a brew with each apply to different plants and take notes.

Yeah. I'll definitely do a little experimentation. Point taken about keeping it simple to start. I can see that there are many potential variables even with a simple tea (brewing time etc). I'd really like to get a microscope, but a good one costs, and money is fairly tight right now.

when im testing new designs, which im actually doin atm. im just using homemade compost, stream water from our property, and a tiny bit of molasses. i would not use unfinished compost. in your second post you mentioned castings, are they a good source? if so thats what i would use until the compost is finished.

OK thanks, I'll avoid the compost for the time being then. For the water I'm using collected rainwater, and the castings are good quality I think. I got them recently, and it's crawling with immature worms.



I'm not sure if that's a good or a bad thing, but the other day when I opened up the tub, it didn't smell very good. Perhaps I should leave it open or let the young worms out? I was thinking of scraping them out and putting them on the compost. I'll do that now I think...

Thanks again for the advice

 

[neongreen]

After more than 48 hours brewing

After more than 48 hours brewing

here's what it looks like

I probably should have stopped and used it sooner. I'll try again tomorrow, and brew for a bit less time!

 

[magiccannabus]

I use a similar type of thinking, but instead I use a 64oz convenience store cup. I just put the fertilizers in a knee-high nylon and stretch it so it dangles the part with the fertilizers right down the middle of the cup. I have an air line I just fish in from the top and weight down with marbles. It's so easy it's ridiculous. Cleans up easily too.

 

[neongreen]

Thats a great idea magiccannabus, although, if I understand your bubbler correctly, the air bubbles would mainly travel up the sides, negating some of the benefit. If you put a rigid ring (like one of my washers, except perhaps stiffer material, if you could find something appropriate) in the nylon, that's just the right size. so that the nylon is stretched out, then the bubbles should have no where to go but through it. That should churn things up even better.

I'm thinking about some radical new designs for bubblers, but they all involve lots of tubing that would have to be assembled and disassembled for cleaning, and I'm not use if it could be made properly watertight without a permanent seal.

Microbeman - I read through your page, and it's a great collection of info. I also downloaded a couple of PDFs, which I'm looking forward to reading. Thanks for sharing.

After reading what you wrote about fish hydrolysate, I'd like to get my hands on some, but I can't find anywhere that sells it here. Is it possible to make it myself?


PS. Forgot to add, when I went to remove my cage from the bubbler, it jammed, which I suspected might happen, so I sanded down the slight rim that was jamming, hopefully enough to make things smoother next time.

Cleaning it was not too hard. I did have to use the shower to get the bits of compost out of the screens (hard to get all of it out but the H2O2 took care of that), but apart from that it was just a case of roll up my sleeve/brush for a few mins and drop the little bits (air-stones + screens) in a solution of hydrogen peroxide. It took me perhaps 20-30 minutes not including soaking time. With practice I could do it in 10-15 I think.

So it works OK as far as I can see. I've got a temperature probe monitoring the temps this time round too. A few hours ago the temperature was 17.5C, and dropping I think.

 

[maryjohn]

I I would love to know the dissolved oxygen compared to a bucket with air pumps. My feeling is that your design has a lower surface area to volume ratio.

So your system has to work much harder to get the oxygen and cannot be scaled up effectively.

 

[Microbeman]

After reading what you wrote about fish hydrolysate, I'd like to get my hands on some, but I can't find anywhere that sells it here

Organic Gem is good as well.

 

[neongreen]

I would love to know the dissolved oxygen compared to a bucket with air pumps.

So would I!

My gut is telling me that it should be higher, since all the surface area comes from the bubbles.

Let me give an analogous example. Human lungs are organs that are designed for gaseous exchange, and the lung surface acts much like the surface of water. If the surface of lungs were flat, lungs would not function as they should, but they are not. The inner surface, is made up of folds of tissue, and those folds are further folded, and so on. This greatly increases the surface area available for gas diffusion to occur over.

In fact, if you stretched out a pair of human lungs so that they were flat, they would cover the area of a tennis court!

Bubbles are analogous to the folds in lungs. They increase the surface area over which gas exchange occurs. Lots of small bubbles vastly increase the surface area available for gas exchange, much more so than having a flat water surface at the top.

I hope Microbeman runs a few more tests, as I'm sure the theory is sound, and there are advantages to be had.

I agree though, that this would not scale up very well, at least with the current design, but I am wracking my brain to try and come up with a design that would scale it up a little, although I doubt a bubbler of this type of design, with a capacity more than 5 gallons would be practical/possible for most growers due to limitations of the design.

 

[neongreen]

Organic Gem is good as well.

Could you elaborate a little please Microbeman? I've never heard of "Organic Gem" before. Thanks.

 

[maryjohn]

No disrespect intended, but your science is way off. Bubbles are not the same as surface area. Exchange of gasses happens mostly at the surface as a result of disturbance, not during the short time a bubble spends at the surface. Your bubbles do not function like the structures in your lungs. You've made the comparison,yes, but that does not make it so.

Were I you I would try to rethink your design to maximize suface area. Thing is, you will come up with a great design: a bucket and an aerator.

 

[neongreen]

No disrespect intended, but your science is way off.

How is the surface of a bubble any different than the surface of water?

Likewise, no disrespect, but I know my science is spot on.

 

[Microbeman]

As I mentioned earlier in this thread;

"as the majority of gas exchange occurs at the water surface to atmosphere interface where CO2 is released. Dissolved O2 (DO2) in water is dependent on the release of CO2."

My science says; The gas exchange means just that; one or more gases is exchanged for one or more gases. In this discussion/topic O2 is being exchanged for CO2. In the case of the lung, the blood arrives at the surface of the lung organelle where CO2 is released and O2(&CO2) are absorbed then infused here and there to cells throughout the body [very simplified]. In the case of water where the goal is to raise DO2 (dissolved O2), there still must be that release of CO2 for the water to attain a higher level of DO2. In natural bodies of water there are plants which exchange O2 for CO2 so some of the CO2 is released into plants. We obviously have no plants in a CT brewer so the only place for the CO2 to be released is at the surface. It is at the surface where the gas exchange takes place so it is at the surface where most DO2 is infused. (there are other considerations such as surface tension disruption factor, etc) Now, having said that, the aquaculture industry has taught us that there is a certain amount of infusion from air diffusers and the tinier the bubble the greater the surface area, the greater the infusion of O2. Also, if the diffusion of air is applied in a column, as in an air lift, the infusion is doubled over a certain height with certain factors (that won't be covered here) but the overall DO2 is dependent on this being applied back to the body of water. This multiplying effect is due to the increased resistance pressure. Therefore the column shaped brewer theory has some merit but the diffusers and air applied to a similar volume of water with a larger surface area would likely produce a higher DO2. If the column were emptied back into another container and broke the surface in the act, then you'd have multiplied
DO2. Sounds kinda like my brewer.

So MaryJohn's science concurs (mostly) with mine.