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Do I really need a false bottom?

Post #1 made 14 years ago
by de5m0mike
Has anyone ever actually had their polyester bag melt in the pot or is this really just a superstition. For some reason I just don't see it happening. I remember seeing someone boil water in a plastic bottle over an open flame and I think, if that cup didn't burn up, how could my bag melt. I'm not scientist but it seems like as long as the bag is in contact with the water/wart then it couldn't melt. I did some quick looking around and I think the melting point of polyester is something like 250º C and I can't imagine anywhere in my pot actually getting that hot.

Post #2 made 14 years ago
by de5m0mike
Ok, so I decided to do a little test for myself. I had some scrap polyester laying around, since I just finished sewing my bag yesterday, and I decided to see if I could melt it. I filled a sauce pan with about 1 inch of water and boiled it over the stove. I put a piece of the polyester in the pot, weighted it so it would touch the bottom of the pan, and boiled it for about 20 min. And what do you know, nothing happened, it did not melt. Not even when held in contact with the side of the pot, the part that is not in contact with the water, it still did not melt. My theory is that since the wart can't get above 100º C without evaporating that as long as the bag is in contact with the wart it can't melt. Of course this was not a very scientific test so I wouldn't really say I proved anything, but I do wonder if we are really just worrying about nothing.

So, in true "Myth Busters" fashion I decided to see what it would take to melt the fabric. I didn't want to ruin a pot so I placed tin foil over my burner and placed the fabric on the tin foil. Of course it melted almost instantly.

So, anyway, unless someone else has experienced a melted bag or can give me a good reason why I should use a false bottom, I'm thinking I'll save a couple bucks and not mess with with making one. Unless of course there is some other reason we need a false bottom other than melting the bag that I am unaware of.

Post #3 made 14 years ago
by hashie
Well done Mike, where would the world be without people like you who take the time to try these things, so that we can all learn.

You raise a very good point with your experiment and I'm in your camp. I can't see that the base of a pot, directly fired, would get hot enough to melt polyester. An electric urn may be a different story?

So the answer to your question is no, you do not need a false bottom. Unless you are going to install a tap on your kettle, with a pick up tube and are happy with all of these extra bits that will need to be pulled apart and cleaned after each brew :)
"It's beer Jim, but not as we know it."

Post #4 made 14 years ago
by Yeasty
FOR SALE:

Stainless steel cake rake. Slightly bent but very clean (Boiled regularly). New string attached. :lol:

Well done Mike. Looks like another Myth busted. I'd guess the result would be the same for an electric element, any of you electric guys willing to give it a go?

Y
Last edited by Yeasty on 01 Mar 2011, 17:48, edited 5 times in total.
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Post #5 made 14 years ago
by PistolPatch
Love your experiment Mike. Good on you :thumbs:

But, this is not a myth :argh:!!!

There are plenty of brewers who have burned and/or scorched their bags. It is most likely to occur when you use a keggle and a burner with a very concentrated flame. It would be very unlikely to happen with a three-ring burner and in my early days, I got slack sometimes and applied heat without stirring and never had a problem with this burner which spreads the heat evenly.

I have had several mates however burn their bag and read forum posts of others doing so. I now play it safe.

What happens is this...

1. You have a bag full of grain sitting on the bottom of the pot.
2. You are boiling the wort. In other words, you are turning water to steam.
3. This steam (gas) gets trapped underneath the grain bag.
4. So, you no longer have the 100 C liquid protecting the bag.
5. This means certain burners can and will make the centre of the bottom of the kettle glow red which is about 400 C which is about 150C higher than the the melting point of polyester.

But Mike, a great topic and I love the fact that you did your best to test this for yourself :champ:.

Note: You don't need a false bottom. You just need to do as The Commentary recommends. Either keep the grain moving when you apply any heat or lift the bag if you have a pulley set-up.
Last edited by PistolPatch on 01 Mar 2011, 18:31, edited 7 times in total.
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Post #6 made 14 years ago
by BobBrews
My first and only bag had two holes melted in the pot. Because I had a double layer I didn't lose much grain to the water. My better half just resewed above the holes an I am still using the same bag. I didn't use a false bottom and I didn't thank it mattered. I now use a bungee cord to keep the bag off the bottom. Bags do melt! It may be rare but they do! I had to grind the plastic scorch marks off the pot bottom. I don't know if it was necessary for the taste of the beer but It bothered me enough to actually do something about it.
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Post #7 made 14 years ago
by de5m0mike
For those who have actually melted a bag, was this during the mash or during the boil. I don't anticipate using the bag for hops or anything during the boil and I wouldn't think it would get as hot during the mash. What do you think?

Post #8 made 14 years ago
by BobBrews
de5m0mike,
For me it was when I was heating the water with the burners blasting away. I dumped the grain bag in and it sank to the bottom. I realized that the burners weren't at low as I normally have them. I didn't think to check the bag at the time because I never have had a problem before. As I pulled up the bag at flame out I saw the damage and I was relived that the bag didn't split open when lifted out.

I now make sure the burners are at the lowest setting when I put the bag in. I also put the bungee cord on as soon as I can to keep the bag off the bottom. I only keep the burners on to make small adjustment to the temperature. I try to go low and sneak up on the temps to hit them. If I were better at figuring out the right strike temps I would not have had the problem. Sometimes my grain is frozen and sometimes ambient temperature, too much thinking for me.

As anyone who knows me can tell you I don't do anything that involves thinking or work. That's why I love BIAB!
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Post #9 made 14 years ago
by PistolPatch
de5m0mike wrote:For those who have actually melted a bag, was this during the mash or during the boil. I don't anticipate using the bag for hops or anything during the boil and I wouldn't think it would get as hot during the mash. What do you think?
The burnt bags will be during the mash or mash-out. So, the burnt bags will occur at temperatures far less than boiling point. Water, even at ambient temperatures is usually 'boiling' (turning to gas) to some extent.

Using a bag for hops will cause you no problem as the hops will not create enough weight to cause the problem I mentioned above.

A burnt bag is rare, maybe one in 70 bags at a guess so you can feel free to play with this. In my mind though, applying heat to a brew, certainly for a beginner, gives you an opportunity to pay attention to your brew, watch it and get to know it. Like anything, sometimes just spending some time looking teaches you a lot more than reading :P.

If you are heating during a mash, agitate it. If you want to do mash-outs, make it a goal to get a pulley system. It's really as simple as that! :party:
Last edited by PistolPatch on 02 Mar 2011, 00:02, edited 5 times in total.
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Post #10 made 14 years ago
by stux
And no you don't need a false bottom. A cake rack will work just as well ;)
Fermenting: -
Cubed: -
Stirplate: -
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Post #13 made 14 years ago
by stux
Yup, mine isn't even as fancy as that :)

Mine uses a spoke and concentric ring design

SWMBO picked it up for me
Fermenting: -
Cubed: -
Stirplate: -
On Tap: NS Summer Ale III (WY1272), Landlord III (WY1469), Fighter's 70/- II (WY1272), Roast Porter (WY1028), Cider, Soda
Next: Munich Helles III

5/7/12

Post #14 made 14 years ago
by de5m0mike
I ran out to Gordon Food Service and picked up one of these. They had the 12 inch pizza screen for $3.00 USD.
Image
I think i'll just use a few bolts around the edges to create little legs to hold it up off the bottom of the pan.

If anyone else has more examples of what they are using I'd love to see them.
Last edited by de5m0mike on 02 Mar 2011, 23:54, edited 5 times in total.

Post #16 made 13 years ago
by shibolet
de5m0mike,
i have been BIABing for over a year and a half now without a false bottom and with no problems whatsoever.
my kettle is electric and my two heating elements are 1500W each. i never had the bag melt or scorch. so you don't realy need a false bottom.
BUT, when i recently added a pump for recirculating the wort during the mash, my bag got sucked down hard onto the heating elements and did scorch. so not i too have a false bottom.
Image
Last edited by shibolet on 09 Jan 2012, 22:07, edited 5 times in total.
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Post #17 made 13 years ago
by joshua
Good Day, From My experience a false bottom or cake/pizza rack is good to have, Kind of like seat belts, TOTALLY useless...Until you need them.
I have had burnt wort on the Bottom of my kettle, due to a hotplate problem, but the false bottom kept my bag from melting.
You can heat the kettle Too Hot and still have cool water!
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Do I really need a false bottom?

Post #18 made 13 years ago
by Lars
I just ordered one of these for my 40l buffalo boiler. Its 32cm diameter and my boiler is 37.5 inner diameter. http://wap.ebay.ie/Pages/ViewItem.aspx? ... ck&emvcc=0
I intend putting legs on it using copper pipe or budvar maybe. Just need it to be about 2 inches off the bottom to sit above tap level. I was thinking of buying stainless steel mesh, making a disc shape slightly larger than the boiler diameter and fixing it to this rack. It would mean I wouldn't need a hop strainer on my tap. Anyone got any thoughts on this?

Thanks

L

Post #20 made 13 years ago
by joshua
Good Day Lars, When I tryed a fine screen(window) I found the goop and Hops plugged the entire surface, and made draining nearly impossible.
I have on "old bag", Nylon, not SWMBO, that I use for hops. I needed to add some weight, to hold the bag down. It works very good for pellet or "real" hops.
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Post #21 made 13 years ago
by argon5000
For what it's worth, I did my first double batch BIAB in a 70L SS pot a couple of weeks back (dry hopped last night) and i used a SS 2mm perforated false bottom and pickup tube in the kettle.

Now, i usually brew with my pumped single tier 3V system and have the SS perforated FB in the kettle as a hop/trub filter prior to cubing/chilling. It works really well, especially when using whole leaf or plug hops (which act as a second layer of filtration). When i left BIAB and went 3V the clarity into kettle was a big change, again something i noted when i reverted back the other week.

So naturally at the start of the boil i noted that the boil was rather murky in comparison to the 3V (it's been discussed heaps before and my conclusion is it probably doesn't effect beer quality) However at the end of boil, when draining to the cube, through the perforated FB, the boiled wort was as crystal clear as ever, straining out alot of hot break, hop pellets etc. The cube had very little trub in it prior to tipping into the fermentor. I believe this is due to the FB (and hops filter).

So whilst a false bottom is not 'necessary' especially to prevent burning the bag, i find i can extract more, clearer wort out of the kettle by using one.
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Do I really need a false bottom?

Post #22 made 13 years ago
by Lars
Hi Argon, I have a buffalo boiler, I'm considering a fb like that. How do you actually get the dome shape that keeps the crap from getting under the fb? Since the buffalo element is in the centre I can't really have anything sitting tight to the centre but that looks like it'd work fine once the dip tube stopped a few mm above the bottom

Thanks

L

Post #23 made 13 years ago
by argon5000
Lars wrote:Hi Argon, I have a buffalo boiler, I'm considering a fb like that. How do you actually get the dome shape that keeps the crap from getting under the fb? Since the buffalo element is in the centre I can't really have anything sitting tight to the centre but that looks like it'd work fine once the dip tube stopped a few mm above the bottom

Thanks

L
G'day Lars, The false bottom I have in there is domed already. Got it from my LHBS.

http://www.craftbrewer.com.au/shop/details.asp?PID=926
Image
Looks like this, i'm pretty sure you'd be able to find one on ebay or someone else on line.

As for keeping stuff from getting under it, the copper tube is pretty stiff and it keeps the FB flat against the bottom of the kettle. I replaced the barb elbow and inserted a threaded rod that i can adjust to minimise the deadspace. There's probably only about 2mm from the point of pickup to the base of the kettle. In a water run it only leaves 500mL behind.
Last edited by argon5000 on 03 Feb 2012, 07:08, edited 5 times in total.
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