Distilling Craft: Ep 003

The Cleaners with Mike Rasmussen

In this episode, we are talking about cleaning. Later in the podcast, I bring in Mike Rassmusen out of Painted Stave Distilling out of Smyrna, Delaware and we talk about how to create products that have a sense of the place your distillery is in.

When talking about cleaning a distillery it is important to discuss TCA first. TCA stands for 2,4,6-trichloroanisole which is a chemical that makes things taste moldy at only 1 – 5 parts per billion. It does this by changing the way your brain’s taste receptors work. TCA is created when common molds are allowed to feed on woody matter such as barrels or cork and create methylated phenolics that then combine with the chlorine to for TCA. Typically, this happens in areas with greater than 80% humidity like your barrel room or floor drains. Once TCA gets airborne it can then make it into your spirit when it is exposed to air, settle into your filter mediums or be absorbed into your corks. Since it is very difficult to remove all mold from floor drains the easiest way to prevent TCA is to ensure that no chlorine cleansers are used in your distillery also it is best to remove any chlorine from your water supply before it is used in any process in your distillery.

Once you’re avoiding chlorine cleansers there are three main types of cleansers; Acidic, Basic or Sterilization/pasteurization techniques. Acidic cleansers are used for removing mineral deposits or metal precipitants. Alkali cleansers are useful for removing organic material and oily residues. Sterilization/pasteurization techniques will prevent infections that are unwanted but do not necessarily remove the physical presence of those contaminants.

For acidic cleansers, my preferred one is Citric Acid it is not as dangerous as say Hydrofluoric acid which has not place in a distillery. Citric acid also can impart citric notes to your spirit if the cleanser is not neutralized or washed away fully. While it is important to remove all of the cleansers after they’ve done their job, in the event of a failure Citric acid’s consequence isn’t terrible. Another common cleanser is phosphoric acid which works well and if improperly removed can also act as a nutrient for yeast. Butyric acid, while not used in cleaning to my knowledge, would be an example of one where the residue, if left behind, would impart a vomit like flavor to your products so if used extra precaution would have to be used to ensure its complete removal. Acids should be mixed at about 10% w/w if they are a typical weak acid. This ensures that the acid is strong enough to do most cleaning jobs quickly while not wasting any cleanser. This is less important is the cleanser is being recycled to a holding tank and the acid content is being maintained but it the cleanser is being dumped after used it is important from both an environmental perspective and financial perspective that the acid is completely spent prior to going down the drain.

The most commonly available Alkali or basic cleansers will be caustic soda which will normally be the least expensive option. The problem with Caustic is that it can cause stress corrosion cracking in the common 305 and 316 stainless steels used in distilleries this is most common when using hot caustic at high concentrations with the safe zone being below 40% w/w caustic at 177°F. Sodium Hypochlorite is a common replacement for the sodium hydroxide (caustic soda) due to it not corroding 316 stainless but should be avoided for TCA reasons above. Caustic is also harmful to people and rates a 3 as a health hazard as it is extremely hazardous for skin contact, eye contact or ingestion and is very hazardous if inhaled. Please use proper PPE when dealing with Caustic.

Sanitizers and cleansers need to be matched to the material that they are trying to clean. For sanitizers, the matching is less important than ensuring proper contact time but in either case, most suppliers will allow you to run a test to make sure that the chemical will clean your particular problem. It is also worth making sure that there won’t be an adverse reaction lots of these chemicals are designed with stainless steel in mind and they can have unforeseen reactions with copper vessels or packing so it’s worth asking some additional questions about copper reactions.  Another way to sterilize your equipment is with steam or extremely hot water, this is basically the pasteurization method that is used on milk or meat. Here are the pasteurization times for Apple Juice from the FDA through PSU and similar numbers can be used to remove bacteria from your equipment.

Surface Temperature °F Pasteurization Time
160 6 seconds
165 2.8 seconds
170 1.3 second
175 0.6 seconds
180 0.3 seconds

These temperatures need to be maintained over the entire surface that could have bacteria for the full length of time but maintaining a tank with 160+°F water isn’t hard for most distillery set ups. The tanks should be monitored to ensure that the temperature is reached and maintained. These temperatures can also be hit while performing other cleaning cycles such as the acidic/basic cleansers above and will reduce the contact time required for those cleansers.

            Contact time is not an exact solution and the easiest way to determine how much contact time is necessary is to test it. Both higher heat and higher concentrations will decrease the needed contact time while lower concentrations and lower heat will take longer. If you are going with lower concentrations it will be necessary to ensure that your cleanser is not spent prior to the removal of contaminant a pH meter or litmus paper will do this job well enough. The other thing that will determine contact time is the volume or size of the deposits. If you are cleaning less often and allowing larger deposits to form prior to cleaning it will take longer for them to be dissolved. Most places have regulations prohibiting high or low pH discharge into the sewer system. The lower limit is typically in the 5-5.5 range while the upper limit is around 12 but check with your local jurisdiction to confirm. You will need to ensure that your cleansers are inside of this range prior to disposing of them this can be done with chemical treatment or dilution. The testing will need to be done in either the cleaned tank or a second tank prior to dumping. This is also useful to ensure that you are using the correct amount of cleanser. If you are utilizing a 10% w/w citric acid but your pH doesn’t change during your cleaning cycle it is probable that you could use less acid and have a lower buffer in the cleanser. If on the other hand your final liquid is completely spent it is probably worth increasing your initial concentration so that your dumped cleanser is in the 6-6.5 pH range to ensure that there was not anything remaining to be cleaned. If you are going to recycle your cleaner then it matters less on the top end since whether you build to a pH of 12.5 or 12 doesn’t matter since you will just maintain at the level but it is still important that your cleanser isn’t coming back at a 7.5 and possibly leaving things still be cleaned in the tank.

            There are several ways to treat your equipment with these cleansers the easiest is simply filling the equipment needing to be cleaned with the cleaner solution and letting it sit for the retention time. The problem with this approach is that the cleanser in the middle of your tank is not treating the walls where the clean problem is occurring and once you’re done you need to dispose of the liquid. A similar solution to filling a tank is to partially fill the tank and then pump the liquid out of the bottom through a spray ball to coat the upper portion of the tank this will require less cleanser to be wasted in the middle of the tank and less to be treated prior to disposal plus if diluting you can do it in place 3:1 if your tank is ¼ full of cleanser. Lastly, there are separate tank systems where the cleanser is kept in a tank either mobile or fixed and is pumped into the vessel to be cleaned and then drained or pumped back to the original vessel. This can prevent a ring from forming at the top of the liquid level and will utilize the minimum amount of cleanser.

With sprayballs it is important to monitor them to ensure that either the spray pattern or spray pattern plus rundown is coating the entire walls of the tank if not you can leave portions that are not being treated. For designed sprayballs they will typically have a GPM range that they are designed to work in with either excessive pressure build-up on the high end or improper coverage on the low end. If your spray balls have not been designed then it is doubly important to monitor their spray pattern in use and possibly rotate the sprayballs either during operation or between cleaning cycles to ensure good coverage. While rotating between cleaning cycles will allow some mineral build up and bacterial residue in each fermentation or other use it is safer than manually rotating a sprayball that is actively spraying cleaning chemicals.

What is the purpose of the cleaning should determine how it’s being cleaned. There is a very little purpose to sanitizing you still considering you are going to get the liquid above the pasteurization point during operations and the vapor portion will be high-temperature ethanol that will kill anything up there. The still needs to be cleaned of any precipitants that formed during distillation so that more can be formed on the clean copper. Also, particularly with gins, the oils and organics need to be removed before they can add flavor to another batch so acidic and alkali cleaning cycles are very important but need to be watched due to potential adverse reactions with copper. The forming of the precipitants and cleaning them away does remove copper from your still or packing material and will eventually cause a pin hole to form and are one of the main reasons that stills do meaningfully depreciate. This is one reason to not use too strong of an acid cleanser to help slow down the acid eating of the copper.

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  1. Sam Harbison says:

    For still that are used to make gin, is there a guideline or rule of thumb on how often or after how many uses it should be cleansed of oils? If you only make one kind of gin would it matter less or not matter at all? I assume if the still were used for gin it would have to be cleaned before it could be used for anything else to avoid gin oils contributing to the flavor of the different alcohol.

    • Really the answer to this is more philosophical than anything else. Yes, if you’re going to be running not-a-gin after your gin you need a very thorough cleaning before the not-a-gin I’ve even heard of some people doing a gin base distillation in between so that any flavors that are picked up can be part of the gin base that starts the next cycle. Generally speaking, it is much easier to have a dedicated still for strong flavors like gin.

      The philosophical part is how often you need to clean a gin only still. I personally believe that you want the start from the same base point each time to ensure that your flavor profile stays uniform. That means refreshing any reactive surfaces (citric/copper) and generally returning the still to the condition you started in. In episode 007 Chip Tate takes the other approach which is only cleaning when required by function (ensuring you’re not putting negative flavors in) and allowing the still to develop it’s own character since after a while you’ll reach an equilibrium.

      How often you’re distilling and how you still is setup will also change the answer if you’re hanging a gin basket above a packet column you’ll need to get the oils out of the packing more often so they don’t start getting bypassed by the vapor. If you’re running a Carter style head and the oils are running into the pot where they are being dumped and diluted by each batch you could clean much less often. I’m sure my vague answer hasn’t been that helpful but there are a lot of little details that matter.

  2. Sam Harbison says:

    When you say 10% w/w, is that meaning 10% of the total weight of solution is acid? So for every 9 lbs water I would need 1 lb weak acid to properly refresh the copper?

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