Pressure filtration on the cheap

[Loveall]

11/13/17 Update: Now recommending using an empty IPA bottle (HDPE) for this. See post #8.

11/8/17 Update: Do not use this device to filter NaOH solutions. More details in post #6 which has a list of chemichal compatibility.

Want to share a simple device that helps me filter rue extractions in case it helps others. After whole seed squeezing and decanting were introduced, some folks have reduced the filtration needs during rue extraction, but for those that still have filtration or decanting difficulties this may help.

Items needed:

-Clear 2L soda bottle (I use Sprite Zero)
-1/2" drill bit and drill
-Filter media (e.g. polyfill from an old pillow or a coffee filter).

Building the pressure filter:

-Drill a 1/2 inch hole on the soda bottle cap. To help keep the drill from slipping, use a nail and hammer to punch out a pilot hole.
-Stuff the hole with filter media. The tighter you stuff the finer then filtration. I've used up to 4 coffee filters without issue.
-You are done.

Operation:

Using a funnel pour the crude rue extract into the 2L bottle.
Screw on the modified cap loaded with the filter.
Turn over the bottle atop a collection vessel. The rue extract will clog the filter in the cap very quickly and only a few drops will come out if you have a rue extract that needs filtering and you've packed the filter by the right amount.
Squeeze the bottle with your grip. According to nasa the average human grip can excert 1000N of force which translate to many atmospheres of pressure on your filter.
Note: Initially I was worried of the filter shooting put. This has never happened to me. The design just works. Sometimes the coffee filter will form a pressurized balloon as you squeeze which is pretty neat.
Liquid will flow as you squeeze. If the filter clogs even with your 1000N of force behind it simply turn the bottle over, unscrew the cap and replace the filter with a fresh one.

Attaching some pictures. Cost is $0 if you can get a used soda bottle and borrow a drill from the neighbors:grin:

Pictures attached.

 

[SnozzleBerry]

Fwiw, you can get a vacuum aspirator for $10 via ebay

 

[Loveall]

Fwiw, you can get a vacuum aspirator for $10 via ebay

Pardon my ignorance, but isn't that just a metal part subset of the aspirator assembly?

 

[SnozzleBerry]

Fwiw, you can get a vacuum aspirator for $10 via ebay

Pardon my ignorance, but isn't that just a metal part subset of the aspirator assembly?

That's the aspirator, afaik. You just need some hoses ($0.35/ft at a local hardware store) and a filtration setup (whether a buchner funnel/flask or a plastic bottle, it's really up to you) to use it. I guarantee it's less of a hassle than cycling round after round through the positive pressure approach.

Hell, if you felt like splurging, you could have a full setup for ~$35 (including the aspirator).

Unless your time is worth $0, the $35 is a pretty negligible outlay compared to the amount of time/effort/engagement the manual approaches take, imo. And if you rig up a plastic bottle instead of the "proper" filtration approach, you're looking at about $11, for significantly less time/effort...you'll just have to Macguyver a bit

Just my $0.02

 

[blue.magic]

Good job :thumb_up:

I use irrigation syringe stuffed with cotton wool.

For larger volumes: vacuum flask, round funnel stuffed with wool sitting on rubber gasket, and a hand vacuum pump from ebay.

I believe you can make such setup cheaply by making two holes in a wide mouth bottle cap, put funnel in one hole and vacuum hose to other and seal with some silicone or glue.

 

[Loveall]

Update: I've been using this pressure filter regularly and it ended up cracking during a base filtration (NaOH):

Turns out soda bottles (PET) are not compatible with NaOH. Other chemichal typically used for rue extractions seem OK (sodium carbonates, 5% HCl/H2PO4/Acetic). See attachment for more details.

Bottom line, this device is not recommended for NaOH filtration :!:. If one is squeezing hard NaOH could spray out. In my case (pictured above) a slow side leak developed first.

 

[Loveall]

Looks like HDPE bottles may be better for this application. Will test them out and report back.

 

[Loveall]

After extensive testing, I now cautiously (warning: contents under pressure) recommend using an empty IPA bottle. Check that these are made with HDPE which is resistant to NaOH. The cap is usually PP which is also resistant. I've used this for multiple acid/base rue filtrations without issues.

There are two ways to load the filter. Push cotton or polyfill into the cap hole, adjusting tightness for very dirty rue extracts. Used filter with cap looks like this,

After that,one can go to nylon, coffee filter, and finally filter paper covering the cap tread. When using paper always reinforce it with a nylon net (e.g. hop brewing bag). Example,

To know when to move to the next filtering stage use the squeeze pressure as feedback. If too hard to squeeze out, unscrew, slide the filter to expose a fresh surface and reload/rescrew (takes only a few seconds). A "backwash" can also be done by "fluffing up" the IPA bottle and forcing air into it which can help increase the flow momentarily. Here is the aftermath of an example when I needed to do this 7x while filtering (probably should have done one more tight polyfill filtering step),

As mentioned above, contents will be under high pressure as the human grip is strong. Keep this in mind and stay safe (safety glasses, etc). I always have the pressure filter cap assembly inside a mason jar,

Keep in mind that if the device fails it can spray liquid at you.

Anyway, this works for me so sharing in case it helps others. My manual vacuum filter is now collecting dust, hand pressure filtration seems stronger and I got tired of it getting stuck in the middle of filtering like in this example,

Just remember to stay safe as the human grip can produce a lot of force (1000N) with both hands. Assuming a 1cm^2 filter opening, that gives 100 atmospheres (=1000N/(0.01m)^2 × (1atm/100000 Pa). Seems too high to believe, did I make a mistake?

 

[CosmicLion]

Well done!

Check out my:

Extremely Effective Homemade [Pressure] Filter Tek [Tek-Pics]

:thumb_up:

 

[Loveall]

Wow CosmicLion, your pressure filter looks amazing! As a newbie I had not seen that post yet, thanks for posting. Definitely looks like your design is better and the IPA bottle may be useful in a pinch.

 

[blue.magic]

Just remember to stay safe as the human grip can produce a lot of force (1000N) with both hands. Assuming a 1cm^2 filter opening, that gives 100 atmospheres (=1000N/(0.01m)^2 × (1atm/100000 Pa). Seems too high to believe, did I make a mistake?

I've managed to crush a glass funnel with the same pump you use. Once the pressure approached 500 mmHg, the glass funnel literally imploded into the filtering flask, leaving shattered glass all around.

I have some respect to these vacuum pumps now and never go over 200-300 mmHg when filtering. If it does not flow, better replace filter than stupidly increase the underpressure like I did.

 

[Loveall]

blue.magic, I think the vacuum filter glass is designed to work with no issues at -600mmHg. Maybe you had a pre-existing crack? Could a chemist enlighten us here?

 

[starway6]

Hey nice two liter filter set up!
This two liter device looks simple enough..but could you please explain the whole procedure for rue extraction..unless..this is the whole procedure?..

What to use first ?...crushed rue seed?...mixed in what water???. [[[maybe boil first ??] and when to add the lye? ... then put contents in two liter bottle with filter system then squeeze?/ and out comes rue extract??? ...or is there more steps to it?? im just guessing..

I would like to know a simple effective way to extract reasonably pure Rue... and building your two liter bottle system is easy enough... just need to know the whole process explaining the need for the lye and how it works...

I have boiled rue seeds several times in past to be left with a crude thick surrup but need to know a better simple way to purifiy it more..

I like the simplicity of the two liter bottle pressure filter though...

 

[Loveall]

Thank you starway6. It can filter pretty bad messes, if one starts with stuffed cotton or polyfill. The pressure you feel when squeezing helps decide on the next filter.

The cleanest starting point with decent yields in my experience is to put the seeds in a fine nylon bag and microwave in a water/vinegar mix inside a glass mason jar for 10 minutes, doing this up to 5x times until the color is clear. Squeezing the bag (I use a pestle) at the 5 minute mark to help get the liquid in/out of the seeds. The Nylon bags I use are rated at 75um pore size, so they result in a pretty clean tea. I'm also looking at using vacuum cleaner waterproof bags that are rated at 0.5um and relatively cheap compared to the other 0.5um materials out there, but I have not tested them yet and I'm not sure if they are 100% food safe.

Some recommend to allow the tea to settle for an extended time in the fridge (days) and then decant the clear layer that forms.

Others like pressure cookers for the extraction, but I've found that the extra temperature/pressure turned my seeds mushy and the resulting tea needed more filtering. This may have been my fault for letting the pressure cooker run too long.

In short, there are many ways of making rue tea and then cleaning it up. I don't think there is one way that is the best for everyone. My approach is to try the ideas that are out there and keep what works for me (and understand that someone else may find a better approach among those same ideas that works for them).

 

[starway6]

Sounds ok....but is this just to make a rue tea ?...

Because when i make rue tea i simply finely crush a couple grams of rue seeds and put them in a double walled fine tea bag.. and steep in hot water like any other kind of tea...

Are you shooting for a ..[later in the process]... purified form of ..[rue crystals] by using the pressure filter/?

I would like to get rue in an easily vaporized form...