ProCaps Are The Answer?!

edited August 2021 in Usage

Hi this is my first post so I wasn’t really sure if I should start my own thread or piggy back on to somebody else’s thread. Apologies for the lengthy post and if it is in the wrong place.

Not even sure if this is a question, statement, introduction or seeking confirmation. Some background first.

I have been using a 4” 4 bubble plate modular still for 8-10 months and whilst I am happy with the final product I feel like there is something not quite right with the process.

The gear:

  • 4x4x3 Tees
  • 50L boiler
  • 2 x 2400W elements
  • Power controller
  • Gate valves on outlets of defleg / PC
  • Parrot

I predominantly run rum (sometimes a whiskey) as a single run. No stripping just run it slowly and take tight cuts. The product then goes on oak for 6 months.

On heat up I run both elements defleg open, once at temp I will drop 1 element to 35-40% and slowly take off fores. Once fores taken I will gradually close defleg to ½. At this setting I will have a take-off approx 2L /hr, so not quite the toothpick stream I have seen mentioned all over the net. Initially I was happy with that – it is a big step up from my 2” homemade pot with multiple strips then spirit run. Now I want to speed things up a bit. If I try push the 2nd element higher I get flooding on the 2nd &/or 3rd plate.

Now the reason I am here, after reading a lot about ProCaps and how it fixes flooding, I managed to get a 2nd hand set from oldmate on gumtree. I ran a sac run last weekend and wow I was able to run both elements at 100% and they wouldn’t flood, not even close (but y’all already knew that). I was squealing like a school girl at a Bieber concert. I did eventually dial the elements down to my normal power settings to see how it compared to the bubble plates. It was a definite improvement but not mind blowing 4-5L like some suggest.

Looks like I need to re-learn my still’s sweet spot. Obviously there is a lot of factors at play but i did read somewhere a figure of 1500w per cap.

  1. In theory run 4500W for the 4” plate with 3 caps. At these numbers what am I likely to get?
  2. Is this a guide for best power efficiency? Hydraulic performance? something else?
  3. Best or highest take-off rate without flooding plates during a longer run?
  4. Best or highest take-off rate without smearing the product?
  5. Because they can handle more power do I have to run them at the higher power?
  6. If 1500W per cap is the optimum / maximum rate what is the minimum if I wanted to run the still slowly. I am guessing the lowest power I can go to without stopping the bubbling?!
  7. Is there something else from what I have or haven’t mentioned which you think might need tweaking to give a better experience?

Thanks Swampy.


  • edited August 2021


    1. I'm not sure exactly what you are asking here?
    2. The best guide will be your pallet. Yours or your sensory awareness team. You'll need to run the system as many different ways as necessary to arrive at the conclusion. And not every kettle charge is necessarily equal. For example, imo a grain based kettle charge is more forgiving than a cane based kettle charge.
    3. On the 4" diameter many users have suggested that 2.5 to 3 lph is the sweet spot for the best outcome. But with respect to collection speed 5 is totally doable. If stripping first and charging with a higher ABV, I do recall 7 to 9 lph being talked about. Plate count and reflux ratios also impact the final outcome. For example Dave Pickerell is known to have recommended an 8 plate still for whiskey. While others think 2 to 6 plates are best.
    4. Not everyone has the same tolerance threshold for the influence of some judicious smearing.
    5. Of course not. The design simply allows for a wider available operating range.
    6. See # 5
    7. There are lots of award winning spirits made with the original SD bubble cap design. Similarly, the same is true for the ProCaps. The outcome depends entirely upon your interpretation. Just because you can run the system harder doesn't necessarily mean you should. The ProCaps are intended to help scale to the next level of production speed based on the diameter of the column. Indeed the inception of SD philosophy is to have a system (or components) that is/are as scalable as possible so that your entire investment is not brought to a screeching halt while trying to increase production capability on a limited budget. ProCaps will allow you to have more compliant hydraulic behavior faster. But you still have to drive the still.

    StillDragon North America - Your StillDragon® Distributor for North America

  • edited August 2021

    Something to be said for the lower liquid level of the original cap design, especially in larger diameter columns where the liquid holdup differences can be substantial.

    I liked the responsiveness of the shallower-cap design, I felt the lower liquid volumes meant adjustments in reflux would show themselves at the parrot far quicker (which would be expected with a larger column holdup, all else equal). But this was on flavored spirit, not neutral.

    On 4 plates, from my own runs, I feel like the deeper liquid bed is around ~5 proof higher output at the parrot (from wash), again, all else equal, and from a strip is good for at least a ~10 proof jump. As such we've had to adjust our reflux temps to compensate for this.

    Another factor, if you are compressing heads, and then opening it up for hearts, it takes a good 2-3x longer to run the plates dry. This is probably contributing to some of the proof increase per run we saw on the procaps. However, on the tails compression, the deeper bed absolutely lets us push deeper into tails than the shallow cap design, and has increased our product yield.

    Sure, the top end of the throughput is higher on the procap, no argument there, and the deeper liquid bed does let you push the still harder and still maintain a higher purity. But, the old cap design is still fantastic.

  • edited August 2021

    Off topic though, back to the original post.

    On your point 7.

    Not sure exactly what your doing to manage your reflux, but if you are just shutting a valve to half without the ability to monitor coolant temperature, you are going to have a hard time repeating runs, or dialing in the still for optimal performance. Odd plate flooding - for me this almost always feels like a subcooled reflux issue pushing the column out of equilibrium.

    Power input is only one half of the equation, balanced by the reflux ratio on the top side. Flooding isn't about power input exclusively, the amount of reflux you are sending back down is the issue. ESPECIALLY, when you are sub-cooling to do it.

  • edited August 2021

    Thank you both for the replies. The cooling water is a 10,000L steel tank around the side of the house in the shade, in winter it does get damn cold. I have today removed the gate valves and replaced with needle valves, i have also installed them on the water inlet lines rather than the outlet lines, i am hoping this will give more control over the amount of cooling entering the condensers.

  • Flow control on the inlet side will not provide any additional control.

    StillDragon North America - Your StillDragon® Distributor for North America

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