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Apologies for posting on a topic that's been well-covered in prior posts, but I can't seem to find an a clear answer on the subject.

Does anyone have sources regarding the safe use of PTFE vs Silicone gaskets for distilling? It's clear from posts that the HD community fully endorses the use of PTFE gaskets and/or the use of PTFE tape-wrapped silicone gaskets but discourages the use of silicone gaskets.

My question comes from the potential leachables / extractables from these two sources. Organic solvents like ethanol (or acetone, etc) can cause swelling and leaching of PDMS (silicone), but with very low toxicity. PTFE has higher tolerance to organic solvents (specifically ethanol, acetone) but with much greater toxicity.

Does anyone have any sound rationale for the use of PTFE vs Silicone? Or possibly both should be avoided?

Thanks for your patience and/or indulgence on this question.

Look up the manufacturers chemical compatibility data for any material you want to use and check it against the various solvents that it will be in contact with during distillation.

Silicones aren’t all the same . That is the problem . There may be a Specific Silicone product out there that is tolerant to everything that passes through a still . Nobody has produced a chart to show what this Magic Silicone product is ...... but iff’n it did exist , as mentioned , there are a lot of Silicones out there . To the average guy , they are all ... Silicone... next thing , there will be roof and gutter silicone and god only knows what else being used .

This is why we have a no Silicone Rule .

Manufacturers' chemical compatibility for both show up as excellent in combination with ethanol. I'm sure that both would perform in service without significant issues.

I'm more concerned about the leachables / extractables than the durability of the material which aren't explicitly covered in chemical compatibility ratings. I'm guessing this would be the concern of most of the HD community as it relates to the use of materials of construction?

Yes , to alcohol , which one Ethanol , what about Methanol , Butanol Propenol etc, now look up compatability with the other few dozen ketones aldahydes etc

I guess my question is not really just about why the "no silicones" but also why the "yes ptfe".

Silicones have very low toxicity and the base material (polydimethylsiloxane) is promoted for use as an antifoam on this forum.

PTFE extractables are highly toxic C8 materials which are known carcinogens.

Is there any rhyme or reason to how the materials of construction are recommended?

I use PTFE because I asked my industrial gasket supplier what materials I could use for my still, thinking that he would recommend silicone. He didn't. He did the research for me and came back with PTFE as the only option, so that is what I use.

I use PTFE because Ive found enough information to convince me that silicone might be stable in alcohols at room temperature, they become less stable at or above the boiling point of acetone, butanol, etc. Its just not work the risk of what china [might] consider a "food safe" silicone.

I think it's not just resistance to hot ethanol that's required.
Last I checked silicone wasn't compatible with ethyl acetate, which comes over at the start of the run.

Any more info on the toxicity of ptfe?

Granted, I've very little knowledge on the subject.

PTFE has been produced historically using PFOA which are known carcinogens. Suppliers in most developed nations have moved toward manufacturing processes that limit the amount of PFOA in the final product. I suppose my concern isn't with high quality suppliers of PTFE, but in products from China, Russia, or other countries without significant regulatory oversight.

Here's a commentary on the subject from the Euroopean Chemicals Agency.

"Globally, PFOA manufacture and the uses of its salts (e.g. APFO) in fluoropolymer manufacture
(e.g. Polytetrafluoroethylene - PTFE) have been identified as the main direct emission sources
of PFOA. These direct emission sources have been significantly reduced in the USA, Europe and
Japan, due to a voluntary agreement between the US EPA and eight of the largest global
fluorochemical manufacturers to phase out PFOA and related substances by the end of 2015.
However, it is important to note, that the manufacture of fluoropolymers is shifting to
countries such as Russia and China, where it is assumed that a large share of fluoropolymers is
still produced using PFOA. This can be seen from (PTFE-based) consumer articles containing
PFOA as residue (up to 5000 ppm PFOA in PTFE mixtures), which are often imported from
outside the EU."

https://www.industrialspec.com/images/e ... om-ism.pdf

Above is a somewhat helpful spreadsheet. * Note that these are ratings are at 64F.
Mods please delete if you feel this is less useful than I thougth it might be.
High heat will obviously have a more adverse effect on the materials. Chemicals are in alphbetical order on the left. Seal materials across the top.

I got EPDM gaskets. Looking at the supplier's chart, it looked like the correct one to get and was only a few dimes more than the other materials.

Bee wrote: ↑Thu Oct 22, 2020 2:31 pm I got EPDM gaskets. Looking at the supplier's chart, it looked like the correct one to get and was only a few dimes more than the other materials.

EPDM is not recommended in the vapor path, same with all other materials except PTFE, or flower paste.

So just to be clear for me.
What exactly is the effect that concerns everyone about silicone? I can see its not recommended but what is the concern that is causing people to say this?
it is going to release a compound that is going to give me cancer? (worse than drinking too much)
or is the concern that it will break down over time and become brittle?
Will it leave a bad taste in the spirit?

Forgive me if I'm asking for too much information but as a parent I have learnt that if you can explain why something is bad it will work much better that just saying "Don't do it".

"Don't smoke" vs "Don't smoke because it will give you cancer and cause you to die a horrible death"

jayka wrote: ↑Fri Oct 23, 2020 10:33 am So just to be clear for me.
What exactly is the effect that concerns everyone about silicone? I can see its not recommended but what is the concern that is causing people to say this?
it is going to release a compound that is going to give me cancer? (worse than drinking too much)
or is the concern that it will break down over time and become brittle?
Will it leave a bad taste in the spirit?

Forgive me if I'm asking for too much information but as a parent I have learnt that if you can explain why something is bad it will work much better that just saying "Don't do it".

"Don't smoke" vs "Don't smoke because it will give you cancer and cause you to die a horrible death"

I'm also interested in why not to use silicon. My new still is sold by a guy who's sold hundreds all over the world and he assures me his silicon seals are perfectly ok for distillation/alcohol/ethanol/methanol/acetone etc. But with everyone on here telling me it's not safe enough I'll buy ptfe seals anyway, they're not expensive anyway

Yeh after reading this I checked out my "purpose built" still and it also has silicone gaskets.
I have made plenty of good whiskey and don't seem to be having any problems.
I find myself being a little reluctant to adding made from carcinogenic material to my still without a proper explanation.
I'm not a reckless guy, I dont even like BPA free water bottles so I'm not so keen on adding a carcinogenic material to my still.

If its just a matter of it breaks down or goes brittle or discolours that's cool I'll get a new $2 gasket when it gets bad.
If its going to make me sick then I'll change it. But so far I haven't seen anything other than "Silicone bad"

So I googled the "chemical compounds of alcohol" "Chemical compounds in whiskey" and also took the few that have been mentioned in this feed and then cross referenced it with the chart also posted here.

The few I could find were
Alcohol: Excellent to slight discolouration
Butanol: Slight discolouration
Ethanol: Slight discolouration
Isopropyl Alcohol: Excellent
Methanol: Excellent

The only one of concern was
Alcohols: Amyl which scored a "D" Severe effect not recommended for any use
I looked this one up individually and from what I could find it has a boiling point of 138.5c so your would need to be going pretty deep into your tails to find this one.
here is a snip on how to isolate it. After all this I just want to say
Don't get me wrong. I'm not trying to sell silicone here. I'm just looking for evidence why I shouldn't be using it and sharing what I could find.

What does it say about ethyl acetate? That's what comes through in fores.
Iirc amyl alcohols also come over during a run. Pure boiling point alone doesn't mean much, some compounds come over even below their boiling point. Relative solubility as well as boiling point matter.

But you do have me wondering about carcinogenics in ptfe now. I bought my seals off aliexpress, so I might swap them out.

Ethyl Acetate is all good "B" Slight discolouration

Amyl Alcohols: all I could find was this
boiling at 131.6 °C, slightly soluble in water, and easily dissolved in organic solvents.
I have no idea what slightly soluble means in this situation.

If silicone has a low toxicity but less resistance to chemical attack and ptfe has a known carcinogen but is much more resistant to chemical attack, then the latter is the better choice as far as I'm concerned.

My gasket supplier's PTFE is manufactured in Italy.

I'm new here, also have this question, but what I've figure it out here is that it is not recomended because of the lack of information about human health safety using different gaskets in distillation

SaltyStaves wrote: ↑Fri Oct 23, 2020 1:25 pm If silicone has a low toxicity but less resistance to chemical attack and ptfe has a known carcinogen but is much more resistant to chemical attack, then the latter is the better choice as far as I'm concerned.

My gasket supplier's PTFE is manufactured in Italy.

But what happens after the attack? that's what I want to know.
if nothing harmful comes out whats the worry?

The bet is that for our application, PTFE will resist chemical attack for the working life of the material and that Silicone won't. Their chemical composition and manufacture are secondary concerns to their performance during their working life.

Think of it like stone fruits that contain Amygdalin. We understand its lurking in there but it doesn't stop us from using them to make booze and tinctures. If it were easily extracted in harmful quantities then there would be far fewer fruit brandies out there.

jayka wrote: ↑Fri Oct 23, 2020 1:51 pm

SaltyStaves wrote: ↑Fri Oct 23, 2020 1:25 pm If silicone has a low toxicity but less resistance to chemical attack and ptfe has a known carcinogen but is much more resistant to chemical attack, then the latter is the better choice as far as I'm concerned.

My gasket supplier's PTFE is manufactured in Italy.

But what happens after the attack? that's what I want to know.
if nothing harmful comes out whats the worry?

No one knows and that's why it's not recomended. It requires scientific research, hplc analysis, in ppm scale at least

You guys are beating a dead horse here.

HDPE for fermentation buckets and PTFE for gaskets is all that's endorsed here in terms of synthetics. You're skirting rule #8 and it ain't worth it.

What you do in the comfort of your own shop is your business, but I would suggest it isn't a good idea to air it here.

Expat wrote: ↑Fri Oct 23, 2020 2:43 pm You guys are beating a dead horse here.

HDPE for fermentation buckets and PTFE for gaskets is all that's endorsed here in terms of synthetics. You're skirting rule #8 and it ain't worth it.

What you do in the comfort of your own shop is your business, but I would suggest it isn't a good idea to air it here.

I'm not trying to convince anyone of anything. I'm just looking for more information that "silicone was made by the boogeyman"

jayka wrote: ↑Fri Oct 23, 2020 4:22 pm

Expat wrote: ↑Fri Oct 23, 2020 2:43 pm You guys are beating a dead horse here.

HDPE for fermentation buckets and PTFE for gaskets is all that's endorsed here in terms of synthetics. You're skirting rule #8 and it ain't worth it.

What you do in the comfort of your own shop is your business, but I would suggest it isn't a good idea to air it here.

I'm not trying to convince anyone of anything. I'm just looking for more information that "silicone was made by the boogeyman"

as a newbie i read this post with some anticipation but little expectation.
i do think it's an important subject, we can all probably agree to use glass, S/S & copper, but with so many modular stills around, the subject of gaskets is still shrouded in mystery, hearsay and rules.
even the chart beforehand does not address different types of material or temps involved in our hobby.
it would be good if there was some real scientific info.
i wouldn't mind paying for quality and buying from selected gasket suppliers/manafacturers, or regularly having to re-new gaskets as required.
how long do epdm and ptfe and silicone resist chemical attack?
i saw a cooking product this morning, proudly advertising "PTFE free!!!"

This topic has run its coarse . Again , there has been no evidence provided that Silicone is as safe as Teflon . It is my understanding that any questions about the toxicity of Teflon are from its manufacture , not from its use .
Until someone can show a Chemical compatabilty chart that proves that Silicone is as good as Teflon , then we shall hear no more talk on the subject .
HD forum is never going to endorse the use of anything other than Teflon until such proof is provided . We will not be held accountable for endorsing material or practices that are considered unsafe or potentially dangerous .

By all means , do as you please in your own sheds if you believe it OK , but do not bring it here .

As this topic has been left open for many days and still no evidence is being supplied , I am going to lock it before a shit fight occurs . We have a lot of good members here , we will not see the plastics debate divide and destroy.

Thanks to deplorable for providing the Chemical compatibility chart .

The other thread has been locked but I found some info and thought it worth sharing. mot trying to drag up old arguements. Here is the link also to the whole article if you wish to read however the important part is in the screen shot.
https://www.mindbodygreen.com/articles/ ... cone-toxic

thought maybe you could post it to the other thread.