Fermcap-S and Evaporation

For my last 3 batches I have been using Fermcap to both control boil over and eliminate the need for a blow-off.

My set up is using a 10 G boil kettle with ball valve to drain. It is a low, wide kettle, not a tall narrow. My pre-boil volume is 8.97G and my batch size into fermenter has always been 6.25 gallons. This has always been spot on with 1.25 gallon boil off and less dead space has always given me my 6.25G in the primary. I do 90 minute boils.

In the last 3 batches with everything staying the same except for the use of Fermcap I have only gotten 5.25G in the primary so I am losing an additional gallon to evaporation. My boil is always a gentle rolling boil, not vigorous and the weather has been pretty consistent during each session.

I have done some research into this without finding anything, I am wondering if anyone else has experienced this and if it is possible that Fermcap is increasing the rate of evaporation somehow.

That is an extra gallon of evaporation, seems unlikely the fermcap would cause that. What about your SG, is it way high and you have to add water? One thing I have started doing is partially covering my boil to reduce the loss but that still wouldn't explain why you lost an extra gallon compared to previous batches.

If you put X amount of heat into your pot, you will lose Y amount of liquid to vaporization. Fermcap-S is not going to change the physics of the situation.

I understand your boil-off has changed; you might want to look at any changse to your burner / gas situation. Sounds like something has caused more heat to get into your kettle. Less wind, etc. Or, less heat is escaping the kettle (warmer ambient temps will increase the boil-off rate due to less loss of heat from the walls of the kettle).

Beerfly said:

That is an extra gallon of evaporation, seems unlikely the fermcap would cause that. What about your SG, is it way high and you have to add water? One thing I have started doing is partially covering my boil to reduce the loss but that still wouldn't explain why you lost an extra gallon compared to previous batches.

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My SG Has been a little high on these three batches so I have adjusted with the addition of water to dilute to the proper SG and raise the volume as well, it's just that i am really at a loss as to what's going on.

This all started with the use of Fermcap. My next batch, which will be a repeat of the second I plan on doing without the Fermcap again to see where it comes in to try and isolate the source but I'm curious if anyone else has had this issue.

I didn't notice any difference in boil off rate when I started using Fermcap. Oh and also, just be careful about this line of thinking,

"I have been using Fermcap to both control boil over and eliminate the need for a blow-off."

I've never had a boil over using Fermcap and I normally add a little extra Fermcap in the fermenter with the yeast nutrient. Things had been so calm for the last year and a half that I was thinking I could probably stop using the blow-off and just slap on an airlock right at the beginning. Thankfully, I didn't implement this plan prior to my latest batch. I woke the morning after pitching to a rhythmic thump coming from my blow-off vessel. When I checked it out it was obvious the krausen had coated the entire headspace of the bucket and there was foam creeping its way through my blow-off tube. That yeast was happy!

I've been using Fermcap in every batch for the last couple years and there has been no change in my evaporation. Keep looking....

Shooter said:

I didn't notice any difference in boil off rate when I started using Fermcap. Oh and also, just be careful about this line of thinking,

"I have been using Fermcap to both control boil over and eliminate the need for a blow-off."

I've never had a boil over using Fermcap and I normally add a little extra Fermcap in the fermenter with the yeast nutrient. Things had been so calm for the last year and a half that I was thinking I could probably stop using the blow-off and just slap on an airlock right at the beginning. Thankfully, I didn't implement this plan prior to my latest batch. I woke the morning after pitching to a rhythmic thump coming from my blow-off vessel. When I checked it out it was obvious the krausen had coated the entire headspace of the bucket and there was foam creeping its way through my blow-off tube. That yeast was happy!

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Thanks, I am aware............. According to what I've read, if you use it in the boil you do not need to add again in the primary and I haven't with no issues. I have also read that if you use it in the primary it increases the hop utilization factor so that needs to be taken into account if that's when it's been added.

Denny said:

I've been using Fermcap in every batch for the last couple years and there has been no change in my evaporation. Keep looking....

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Yeah, this is what I've been hearing from my inquiries so I will keep looking into this, I've evaluated everything else and this is the only thing that's changed so I'm a little lost..............perhaps in more ways than one...........

passedpawn said:

If you put X amount of heat into your pot, you will lose Y amount of liquid to vaporization. Fermcap-S is not going to change the physics of the situation.

I understand your boil-off has changed; you might want to look at any changse to your burner / gas situation. Sounds like something has caused more heat to get into your kettle. Less wind, etc. Or, less heat is escaping the kettle (warmer ambient temps will increase the boil-off rate due to less loss of heat from the walls of the kettle).

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I agree and understand however I have brewed 2 of the same batches under the same conditions using the same equipment and the fermcap batch experienced greater boil off. I know that the product reduces the overall surface tension of the wort and am wondering if that is in play. I am trying to email R&D as well as a competitor's product to see if I can get a reply. I'll let you all know if I find something out.

Humidity plays a huge roll in boil off- perhaps it's drier now and you're boiling off more than in the summer?

Or, if you really want to blame the fermcap, you could consider that since you're not risking boiling over that you're boiling water than you used to.

There are no other possiblilities.

I have used Fermcap-S is some brews and none in others I have seen no difference in boil off rates. I doubt very seriously that the Fermcap has anything to do with this phenomenon.

I would think that something else has changed. Maybe just that it is getting warmer!

duboman said:

Thanks, I am aware............. According to what I've read, if you use it in the boil you do not need to add again in the primary and I haven't with no issues. I have also read that if you use it in the primary it increases the hop utilization factor so that needs to be taken into account if that's when it's been added.

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I haven't found either of those to hold true for me.

Thanks for all the replies, not looking to blame a product, just trying to figure this thing out, while a await a reply from R&D( assuming I might actually get one) I'm going to revisit my notes , volumes, etc and see if there is something I'm missing.

Both batches were brewed on the Same everything, both days were 72-74 degrees and I brew just inside my garage so ambient is relatively the same as well as wind.

I know all of you that replied are experienced brewers with a lot of batches under your belts and have all replied the same so.........must be me

duboman said:

According to what I've read, if you use it in the boil you do not need to add again in the primary and I haven't with no issues.

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I never used to add it in the fermenter, but I also used to just dump my entire boil kettle contents in. Now that I run it out of a spigot and leave a lot of the trub behind, I add a little extra because I have no idea how fast the stuff settles out in the wort while it's chilling. It's probably not necessary. The stuff does work, but just be ready for that odd batch that springs up when you suddenly decide it's safe to skip the blow-off tube.

duboman said:

Thanks for all the replies, not looking to blame a product, just trying to figure this thing out, while a await a reply from R&D( assuming I might actually get one) I'm going to revisit my notes , volumes, etc and see if there is something I'm missing.

Both batches were brewed on the Same everything, both days were 72-74 degrees and I brew just inside my garage so ambient is relatively the same as well as wind.

I know all of you that replied are experienced brewers with a lot of batches under your belts and have all replied the same so.........must be me

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Keep in mind that the same temperature does not mean that the humidity will be same.

EDIT: Also, if you just got a fresh tank of propane you might boil off a bit more compared to a tank that's low.

So believe it or not I actually received a reply from the Biochemist in the R&D department with a complete explanation regarding the use of Fermcap-S. He also happens to be a very accomplished brewer and member of the ASBC

In summary of what proved to be a lengthy dissertation, Fermcap-S or any anti foam agent is a silicone based substance that effects and reduces the overall viscosity of the wort and its proteins.

By performing this function in the reduction of viscosity it also has the ability to indirectly affect the rate of evaporation once it has been added to the boiling wort if the vigor of the boil remains unchanged. To decrease this overall effect, the vigor of the boil can be reduced to minimize the potential increase in the rate of evaporation from use of this type of product.

He stated that the reason most of the brewers I have spoken with have not experienced this issue is most likely to due to the fact that they have been more consistent in the management of their boil and thus have a more consistent rate of evaporation.

So, in summary, the use of an anti foam agent can indirectly affect the rate of evaporation if the vigor of the boil is not properly managed after its addition to the boil.

All in all I have found this to be quite interesting in my quest of brewing better beer and managing my process

While this may be true, I always set my propane at the same setting on the valve, I did this before foam control, I did this after foam control. If there was any change in the evaporation it was so small to be unnoticeable.

You are getting a full gallon extra now at what you're calling a gentle rolling boil. It sounds to me that in order to manage your boil to negate the extra boil off, you'd essentially have to turn down your heat to a point where you are no longer boiling.

I suppose you can adjust to collect more runnings prior to boil. I could maybe imagine that a minor difference that I don't notice in my system is noticeable in yours, but you've almost doubled you evaporation rate. I mean how wide and shallow IS this kettle of yours?!?!

Shooter said:

While this may be true, I always set my propane at the same setting on the valve, I did this before foam control, I did this after foam control. If there was any change in the evaporation it was so small to be unnoticeable.

You are getting a full gallon extra now at what you're calling a gentle rolling boil. It sounds to me that in order to manage" your boil to negate the extra boil off, you'd essentially have to turn down your heat to a point where you are no longer boiling.

I suppose you can adjust to collect more runnings prior to boil. I could maybe imagine that a minor difference that I don't notice in my system is noticeable in yours, but you've almost doubled you evaporation rate. I mean how wide and shallow IS this kettle of yours?!?!

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I am not knowledgeable enough to argue with a Biochemist, nor experienced enough to dispute what I am hearing from far more experienced brewers than myself, only relaying the information I received and putting it out there for consumption.

The kettle I am using, and I do not have it in front of me, is as wide as it is high and is 10 gallons so I know that the surface area plays in the evaporation rate as well as temp, humidity, rate of boil, BTUs per minute, etc.
I have been using this set up for the last 10-12 batches since I upgraded my AG setup. I use a calibrated brew stick to measure all my kettle volumes and have never had a problem with my mash volumes. In my winter brew sessions I was still consistent with my output even though it was colder and the air was drier than it is now so I was surprised with the decrease in the batches that I started using Fermcap which is what prompted this thread.

Having received responses from all of you with greater experience and the Biochemist it is obvious that something else is in play.

Question I have-How much Fermcap are you using for a ten gallon batch or how many drops per gallon of wort is being used. I was told 2 drops per gallon which is equating to 17 drops for my volume. I am wondering if I am using more than necessary and perhaps this is coming into play?

Perhaps my perception of a rolling boil is actually greater than a rolling boil as well. Obviously I have to revisit my brew day and boil process in greater depth as it is obviously not an issue with the product, unless, of course I am using way too much.

Appreciate all the feedback and if there is possibly something else I am missing let me know.

I hate to do this, but I disagree with the "biochemist". The heat of vaporization is the amount of energy (heat) that is required to turn an amount of water to vapor. If you put one chunk of heat into the water, a chunk of water turns to vapor.

I seriously doubt that the Fermcap-S is changing the heat of vaporization of your wort.

duboman said:

...only relaying the information I received and putting it out there for consumption.

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That's definitley the point of the forum!

duboman said:

Perhaps my perception of a rolling boil is actually greater than a rolling boil as well.

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I'm wondering if, since using the Fermcap, you're turning up a a little more and, since the surface isn't a foaming mess, you're not realizing the heat is higher because the surface looks gentler? I don't know, a full gallon seems like a HUGE jump too me.

@passedpawn: This is correct and was stated by the chemist, however he pointed out that because the the viscosity of the wort has been altered there is the 'potential" indirect effect of increasing the evaporation rate if the rate of boil is not managed. I would have copied and pasted his complete reply to me but it was several pages long
Fermcap S is not going to affect the temperature of the boil, nor is it going to directly affect the evaporation rate, it has the potential to indirectly affect the evaporation rate based on how the boil is controlled after the addition of the Fermcap. The temperature at which a liquid boils ie its boiling point, is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid.

@Shooter: I love this forum!
I am considering this idea as well since without the foam the surface of the boil appears far different. A full gallon is a huge loss considering that is my normal evaporation loss which I have aready accounted for in my volume calculations.

I boil 8 gallons in a pot that is also as wide as it is tall, no Fermcap and I evaporate 1.5 gallons between boil and cool down. You are boiling 90 minutes, Fermcap or not you will probably lose that much.

How about an experiment? Smaller pan maybe 2 qts of plain water and boil for say 30 minutes and record what's left. With the stove still at the same heat refill and do it all over but use Fermcap on this boil. Somebody with some Fermcap should do this and post results.

Beer fly, thanks, I've actually considered doing this experiment if I get some time and yes my typical boil off has been 1.25 gallons I've over 90 minutes. I'm in Chicago and you're in MN so I'll assume you're a bit colder and drier than I.( weather that is )

I'm planning another batch of the same beer next weekend so I hope to get the test in prior.

Just trying to get as much input as possible so come brew day I can dial everything, take notes and isolate what's going on.

I just used fermcap to boil 10.5 gallons in my 11 gallon pot (man was that fun). Have to say it worked like a champ no foam at all just a whole lot of bubble action. Evaporation was not affected at all, same as always about a gallon an hour.

Beerfly said:

I boil 8 gallons in a pot that is also as wide as it is tall, no Fermcap and I evaporate 1.5 gallons between boil and cool down. You are boiling 90 minutes, Fermcap or not you will probably lose that much.

How about an experiment? Smaller pan maybe 2 qts of plain water and boil for say 30 minutes and record what's left. With the stove still at the same heat refill and do it all over but use Fermcap on this boil. Somebody with some Fermcap should do this and post results.

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So I played Science guy yesterday and conducted an experiment. I placed two identical pots in two burners of my stove. Into each pot I put 2 liters of water and brought both to a boil and they both reached a boil within 30 seconds of each other (timed). Into each pot I added 1 cup Extra Light DME to create a wort, in one pot I added 1 drop Fermcap-S and left the other pot alone as the control. Each burner was set at the same position and flames appeared to be equal. I used a large enough pot to account for not having to reduce heat on untreated pot for boil over concern.

I boiled each pot for 30 minutes and turned off the heat. I then filled my large sink with cold water and placed both pots in the sink to cool to 65 degrees, uncovered. Both pots reached 65 degrees within 1 minute of each other.

Poured each pot into calibrated, sterilized mason jars (To save for my next starters). The pot that contained the Fermcap-S yielded Approximately 75ml LESS wort.

So...........it appears that Fermcap does have the indirect ability of increasing the evaporation rate of a boil but it also appears to have a very minimal effect if factored up to the size of a typical boil volume

I now also have a family that thinks I have completely lost my marbles an am becoming a little too OCD with my brewing obsession!

No, I'm sure your family thought you lost your marbles long ago LOL. Glad you did the experiment, we could debate all day long but this is more concrete. Just to let you know, I have began boiling off extra water in my last two batches, it's probably due to the difference of the season.

Beerfly said:

No, I'm sure your family thought you lost your marbles long ago LOL. Glad you did the experiment, we could debate all day long but this is more concrete. Just to let you know, I have began boiling off extra water in my last two batches, it's probably due to the difference of the season.

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Ha Ha, absolutely! I too have always experienced changes in boil off due to the weather as well but I've always been able to take that in to account to some degree. The thing that sparked this though was the fact that I brewed the two identical batches one week apart with very similar weather and both in my garage, one used Fermcap, one with out. I'm off to find my marbles.............

So after relaying my experiment back to the real Scientist I received some additional information:

I did do a little more digging today and learned something interesting – the surface tension of a liquid affects the evaporation rate of the liquid. A liquid with a higher surface tension evaporate more slowly than a liquid with a lower surface tension. Surface tension is responsible for foam stability – the greater the ST the more stable the foam and antifoams week by reducing surface tension. There it is possible that your antifoam use is resulting in greater evaporation as it has lowered the ST of the wort. I still think that boil vigor as described in my previous email is the primary cause of the difference you are seeing in your brews.

In addition:
One thing you do need to be aware of is that Fermcap S is a silicone based antifoam (dimethyl poly slioxane). Birko sells a silicone based antifoam to brewers (Birko AF100) however we strongly discourage its use in beers that are not clarifies by filtration or centrifugation. The FDA has limits on the amount of this material that is allowed in food. Here is a comments from Dana that was posted on a probrewers forum:

"Brewers should not use silicone-containing antifoam for unfiltered beers. The FDA allows active silicone to be used up to 10 parts-per-million (ppm) but stipulates that the silicone must be removed prior to packaging by either filtration or centrifugation. In the case of unfiltered beers, use a food grade, non-silicone antifoam. We sell a food grade, canola oil based antifoam that works well for this purpose and has an added benefit of being yeast-friendly at the same time. Look for my article on antifoams in the brewery in the July/August issue of The New Brewer. ( this was from Dana Johnson Brewery Technical Representative BIRKO Corporation Henderson, Colorado www.birkocorp.com)

duboman said:

So after relaying my experiment back to the real Scientist I received some additional information:

I did do a little more digging today and learned something interesting – the surface tension of a liquid affects the evaporation rate of the liquid. A liquid with a higher surface tension evaporate more slowly than a liquid with a lower surface tension. Surface tension is responsible for foam stability – the greater the ST the more stable the foam and antifoams week by reducing surface tension. There it is possible that your antifoam use is resulting in greater evaporation as it has lowered the ST of the wort. I still think that boil vigor as described in my previous email is the primary cause of the difference you are seeing in your brews.

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There is a big difference between evaporation and vaporization.

Evaporation happens at the liquid-air surface, and I have no doubt that the Fermcap-S affects that. However, it's a minor player in the liquid you lose over an hour of a boil.

Vaporization happens at the bottom of the keg (if using a burner) or along the surface of the heating element (if electric). In the case of vaporization, the water turns to gas well before it gets to the surface of the pot.