Building Carbon Filter help

[SheepDale]

Hi all,
I am really sorry as this is going to be a long post, but I need your help.

I want to build my own activated carbon filter to polish my spirit. I have studied the ‘paper’ from Gert Strand that was passed to me from a member of this group. I understand fully the basics, but have seven follow up questions that I need help with please.

1. Who is Gert Strand? Is he a professor or a scientist and has some background into the science of carbon? I ask as I was told to be wary of sales people as they just want to sell you their things. In the paper Gert tells us we should use the “Prestige activated carbons” which can be purchased at his shop. I don’t know who Gert is, so to me this just looks like another salesperson trying to sell me things so he can make money.

2. Does anybody in here use the Prestige activated stone carbon, 0.4-0.85 mm? If so, what do you think of it?


I would like to try and do the double polish by using pulverized carbon before I use ‘dry’ carbon. I would distil, then water down my ethanol to 45% with purified water, then put in 4g of pulverized carbon per litre of ethanol. I would shake the container 4 times within a 24-hour period, then leave it for 24+ hours so the carbon all falls to the bottom. Then I would syphon off the ethanol so it is ready for the next stage (which is to put it in a tube of activated carbon).

3. I understand that not all activated carbon is the same and you have to make sure that what you use is the best you can get. I haven’t though read anything about different qualities of pulverized carbon. I assume it matters and there are good ones out there, but does anybody in here use it and if so what company would you recommend ?

4. I can’t actually find “pulverized carbon” in any shop, everybody though does sell “liquid carbon”. I assume this is the same thing, just a different name?

I understand that the activated carbon needs to be put into a stainless steel saucepan with hot or boiling water, mixed and then left to settle. Then syphon off the water, fill it back up with hot or boiling water, mix it, and leave to settle. This process should be repeated 4-5 times. On the 5 time, it should be left for 24 hours. After 24 hours, get rid of the excess water so the carbon is ready to fill the carbon tube.

To build a carbon filter tube, you need to know the dimensions. Gert said “Alcohol normally needs 1.5 meters. It does not matter if the layer (the length of pipe used) is higher, but if it is too thin, then purification will not take place. The pipe must be at least 38 mm in diameter otherwise a “wall effect” will be created and the alcohol runs past the carbon along the wall, without being purified.”. Understood. 38mm wide minimum and also 1.5 meters high minimum.

I am a bit confused over where Gert says “To describe how good this “pre-wetting” method works is easy. To purify 5 liters of alcohol 40-50% one normally needs 1 tube 40 mm x 1.5 meter, then one more to take the last 10% volatiles that remain (this can be used again next time as first filtration). With the pre-wetting method, the same can be done in one filtration in a 1-meter tube, sometimes shorter.”

5. When he says “pre-wetting” does he mean the washing and soaking of the carbon in hot water which I talked about in the previous paragraph?

6. Can somebody explain what he means by “then one more to take the last 10% volatiles that remain”. Does he mean the last bit of spirit that is ‘trapped’ in the tube right at the end?

7. If I am correct on what the pre-wetting means, when he says “With the pre-wetting method, the same can be done in one filtration in a 1-meter tube, sometimes shorter.” So does that mean the filter tube doesn’t need to be a minimum of 1.5 meters long if you pre-wet/soak the carbon?

I understand about filling the carbon tube with water before adding the carbon so that there are no air pockets and once done to knock the tube a bit to compact it. Then once the carbon is in, flush it with 4-5 litres of warm water and then once done add the ethanol to the pipe.

Flow rate is also extremely important so extra filter papers and a ball tap on the end would help sort this.

For the flow, Gert says that it is measured in “Bed volume per hour (HSV, Hourly Space Velocity)”. I couldn’t find any reference to this on the internet, so not sure how to calculate it. Does anybody in here know what it is and how to convert that to something most people could understand?

He did though say this “For a pipe holding 1.7 liters, the maximum purification occurs at 4 dl per hour if the pipe is approx. 40 mm wide and the carbon grain 0.4-1.4 mm in size.”

When Gert says “4dl per hour” I think he means 4 deciliters which converts to 400 millilitres (my measuring jugs don’t have deciliters on them). If we change the ratio, it means we should get 100ml of polished spirit every 15 minutes. If we have 8 Litres of spirit to polish, it should take around 20 hours to filter.

The tubes I am looking to use will be either the 38mm or 51mm (probably will be the 51mm as the wider it is the shorter the pipe should need to be) stainless steel Tri Clamp sort with PTFE gaskets. Below is the design that I am looking to create. If Gert says a 38mm pipe would need to be 1.5 meters long the volume would be 1.7 Litres. If though I used 51mm diameter piping, I could get 1.7 Litres by having it 0.85 meters long.

Design - 1 - Ver 0.1.png

So to summarize, I will use liquid carbon to treat my 45% spirit once it has been distilled and watered down. I will then polish it using 0.4-0.85mm Prestige activated stone carbon in a tube that has multiple filter papers + a ball valve tap at the bottom output to slow the output to 100ml every 15 minutes (or slower). The tube would be 304 stainless steel with a diameter of 51mm. The height/length of the tube is the only thing in contention. I want to use the smallest tube possible, so would it have to be 1.5 meters long or would 1 meter be ok, or could it be a little shorter, and if so, how long?

Thank you very much to all those who can assist me.