BIAB Bag Materials/Design - Pros and Cons

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dick
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Post by dick » 6 years ago

CanBrew wrote:I have a question to add. A fellow in my brewing group expressed concern/speculation about breaking down of the material in a hot, low pH environment. He was wondering:

(a) to what degree the amines leached out of the material
(b) what they might do (I presume by this he meant to the drinker, accumulation in the body that sort of thing, do they affect or even make through the fermentation phase)

Can someone help me with this information?
Actually I don't think there are any amine groups in polyester. You aren't getting mixed up with polyamide?

What can happen to polyester is hydrolysis of the ester. In such a case, the ester link is broken and part of a water molecule is added to each end of the split, putting an alcohol and a carboxylic acid functional group at each end. I wouldn't think this is going on to any significant degree whatsoever during a mash.

I don't have an answer to your question but one thing to note is that plastic soft drink bottles are made from polyester and these bottles have drink in them for months. You would hope that there isn't anything leaching from the bottle into the drink.

Cheers
Dick
Last edited by dick on 21 Mar 2011, 13:14, edited 5 times in total.


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Post by stux » 6 years ago

dick wrote:one thing to note is that plastic soft drink bottles are made from polyester and these bottles have drink in them for months. You would hope that there isn't anything leaching from the bottle into the drink.

Cheers
Dick
Cool, didn't know that PET == Polyester

"Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate (PET)."

http://en.wikipedia.org/wiki/Polyester" onclick="window.open(this.href);return false;
Last edited by stux on 21 Mar 2011, 16:51, edited 5 times in total.
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Post by spog » 6 years ago

g,day fella's, in regard's to bag design,agitation of the wort and cleaning.
how about a tag sewn on the inside bottom of the bag that can have a cord/stainless steel trace looped through it,this cord/trace can be attatched to your lifting system or clipped out of the way and used as an agitator simply by pulling/lifting the cord when required to "circulate" the liquore.
also when finished brewing this loop can be used to hang the bag inside out on the clothes line for cleaning or drying .....cheers.....spog......


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Post by stux » 6 years ago

I thought of adding a tag on the otherwise to tie to the cake rack...

Havent tried if yet tho
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Post by smyrnaquince » 6 years ago

I'll try tagging on to this thread rather than starting a new one...

Instead of a bag, why can't I just take a sheet of voile, push it down inside the kettle, and let the edges drape around the outside of the kettle? No sewing involved. Yes, there would be fold inside of the kettle, but would that be a problem? When the mash is done, pull the edges together, tie a string around them, and lift.


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Post by CanBrew » 6 years ago

Well, short answer is that you can. It sounds awkward though.

I find the material doesn't entirely sink so it could be really unmanageable. Having a drawstring to keep the bag secured to the pot and keep it from falling in save you a bunch of work (maybe even some extra clips since my bag fell in on my last brew :( ). The drawstring also helps contain everything when lifting it out of the pot.
smyrnaquince wrote:I'll try tagging on to this thread rather than starting a new one...

Instead of a bag, why can't I just take a sheet of voile, push it down inside the kettle, and let the edges drape around the outside of the kettle? No sewing involved. Yes, there would be fold inside of the kettle, but would that be a problem? When the mash is done, pull the edges together, tie a string around them, and lift.
Last edited by CanBrew on 27 Jun 2011, 04:27, edited 5 times in total.


stux
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Post by stux » 6 years ago

smyrnaquince wrote:I'll try tagging on to this thread rather than starting a new one...

Instead of a bag, why can't I just take a sheet of voile, push it down inside the kettle, and let the edges drape around the outside of the kettle? No sewing involved. Yes, there would be fold inside of the kettle, but would that be a problem? When the mash is done, pull the edges together, tie a string around them, and lift.
Lots of mini-biabers do in fact do this

Be careful not to spill the grains into your kettle
Last edited by stux on 28 Jun 2011, 00:28, edited 5 times in total.
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Post by smyrnaquince » 6 years ago

stux wrote:Lots of mini-biabers do in fact do this

Be careful not to spill the grains into your kettle
Mini-BIAB is what I had in mind.

Thanks!
Last edited by smyrnaquince on 28 Jun 2011, 01:10, edited 5 times in total.


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Post by BrickBrewHaus » 6 years ago

smyrnaquince wrote:
stux wrote:Lots of mini-biabers do in fact do this

Be careful not to spill the grains into your kettle
Mini-BIAB is what I had in mind.

Thanks!
It's certainly doable, did it for my first couple of mini-BIABs. Like stux said, just be sure to carefully gather everything to avoid spilling grains into the kettle.
Last edited by BrickBrewHaus on 28 Jun 2011, 07:15, edited 5 times in total.


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Post by DABEER » 6 years ago

I was on the web killing time and stumbled across this website. It's a solid looking bag with handles and it is designed specifically for BIAB. It's in the states so shipping to Aus. or NZ may not be worth it but who knows. It's $35.00 US, it's better built than mine and I have $27.00 US into mine, so it's not so far off from DIY costs. Give it a look and let me know what you think.

http://brewinabag.weebly.com/order-a-bag.html

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Post by hashie » 6 years ago

That's a nice looking bag DABEER, perfect for our American brewers.

Not sure I agree with you on costs. Mine only cost $6.50 for the material and I hand stitched it myself. I guess if you paid a seamstress to run it up for you, your costs would be larger.
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Post by DABEER » 6 years ago

Yeah Hashie, I would have been in the same $ range myself, but everyone I knew that could sew had broken sewing machines. I had a hard time finding somewhere to get it done and finally found a place (Commercial Laundry). That cost me $20 right there and I think I spent the same amount for the Voile as you, something like $6.50. So by the time I had a bag, I was in the $26.50 range. If I was to do it all over again, I think I would just purchase this one, it is much better than mine, reinforced edges, extra strong stitching, handles to aid in lifting. Just all around better and about $10 more than I have invested. I may buy one just in case, so I have a back up if needed.

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Post by hashie » 6 years ago

Always handy to have a back up bag dabeer. I have a spare, just in case. Eventually it will become the full time bag, but for now it just sits, waiting it's turn :)
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Post by Michaelvw » 6 years ago

I just looked at the images for bag design (http://www.biabrewer.info/viewtopic.php?f=53&t=37) and was wondering about the reason for having a tappered bag versus just a cylinder style. What are the advantanges of a tappered bag?

I want to make a bag as the one I purchased had holes that were too large and therefore let through too much grist. Still worked out but wasn't ideal.


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Post by datamichael » 6 years ago

Can someone explain the formula posted in the FAQ regarding how to size the material for constructing a bag?

The post states: "Get your measurements from your kettle and cut your material to the following formula..

top = (kettle top circumference x 0.5) + 15%
height = kettle height + 15% + 2.5cm (1”) for drawstring or elastic.
base = kettle base diameter – 15%"

I am a bit "math challenged" so forgive me if I muck this up. The first line "(kettle top circumference x 0.5)" is basically dividing the circumference by two and adding 15%. I don't understand the division. Wouldn't it be way too small? I would think you'd just add 15% to the circumference.

Thanks!

Michael


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Post by Pat » 6 years ago

It is a little unclear Michael so we'll re-write that post at some stage. However, you may have missed that the post says you need to cut two pieces of material with your quoted dimensions and then sew them together.

The bit that is probably worrying you is the first and last bit. An alternative is...

1. Measure the diameter of your kettle (edge to edge).

2. Multiply that by 3.14159

4. Multiply that by 1.15

That will be the width of the top part of one of the two pieces your bag.

The bottom of your bag pieces should be the above multiplied by 0.61.

I suspect that this is not very helpful so ask more questions. We probably need to create a spreadsheet for this.

Cheers,
Pat
Last edited by Pat on 19 Jul 2011, 23:52, edited 5 times in total.
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Post by datamichael » 6 years ago

joshua wrote:Good Day, It is my understanding the 0.5" is so the bag is slightly larger than the kettle. The 15% is for the the double stiched and folded sewn seam. The taper just makes it very easy install the bag, especially if it is full of grain!
But multiplying by .5 *reduces* the size, correct?

Michael
Last edited by datamichael on 19 Jul 2011, 23:54, edited 5 times in total.


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Post by datamichael » 6 years ago

Pat wrote:It is a little unclear Michael so we'll re-write that post at some stage. However, you may have missed that the post says you need to cut two pieces of material with your quoted dimensions and then sew them together.

The bit that is probably worrying you is the first and last bit. An alternative is...

1. Measure the diameter of your kettle (edge to edge).

2. Multiply that by 3.14159

4. Multiply that by 1.15

That will be the width of the top part of one of the two pieces your bag.

The bottom of your bag pieces should be the above multiplied by 0.61.

I suspect that this is not very helpful so ask more questions. We probably need to create a spreadsheet for this.

Cheers,
Pat

Ahh! OK Thx!

That makes more sense.

But to make a tapered bag out of two pieces,wouldn't you need on piece for the cone, larger at the top, and then a circle for the bottom?

Thanks!
Last edited by datamichael on 20 Jul 2011, 00:02, edited 5 times in total.


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Post by CanBrew » 6 years ago

Michaelvw wrote:I just looked at the images for bag design (viewtopic.php?f=53&t=37) and was wondering about the reason for having a tappered bag versus just a cylinder style. What are the advantanges of a tappered bag?

I want to make a bag as the one I purchased had holes that were too large and therefore let through too much grist. Still worked out but wasn't ideal.
The advantage of the tapered bag I like best is that it helps to direct the liquid into the pot when draining the bag. The square shape I tried at first tended to drip from the corners down the side of my pot. It is also easier to sew up than a cylinder.
Last edited by CanBrew on 20 Jul 2011, 01:18, edited 5 times in total.

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Post by hashie » 6 years ago

datamichael, if this tapered bag business is doing your head in, you might like to do what I did.
I took a single piece of voile, large enough to make a bag (1.5-2 metres), folded it in 1/2 and cut the bottom into a semi circle. After stitching the seam the bag looks like an elongated capitol D.
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Post by Ralphus » 6 years ago

One thing I'd like to add to the discussion is that the FAQ at the top of this forum emphasizes that you need a bag:
The bag is a critical part of the BIAB process. You need to have a bag that is of the right material, size, shape and strength.
Which is not entirely true. Long term, yes a bag is probably a good idea. But for a starting BIAB'er all you need is a large square of voile mentioned earlier in the thread. This reduces the barrier to entry for BIAB even further.. and I think it's something that should be mentioned perhaps in the FAQ or The Commentary to help out first timers.

A 1m x 1m square of voile is easy to get and very low cost ($3 here in Canada at Fabricland) and it's been perfect for my first two batches. I trimmed it a little and have been using two bungee cords to secure it to the pot. It's rock solid, easy to tie up and hoist - and has an advantage that it's great to clean as there are no seams or corners for particles to get caught or embedded in.

Long term I think a bag makes great sense.. but for first timers.. keeping this already simple premise - simple.. seems like a good thing.

Ralph
Last edited by Ralphus on 25 Jul 2011, 10:21, edited 5 times in total.


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Post by Josh » 6 years ago

What would be the disadvantages of making a bag as follows:

A tapered cylinder, like a cone with the tip cut off. So a profile shot of it would look like the suggested shape of the pillow slip style bag. But more like the middle picture in the suggested styles. I would make the base a circle, 15% smaller than the base of my kettle. The top would be a circle, 15% wider than the lip of my kettle.

I don't think this bag would be too hard to make. It's only two shapes and two joining stitches plus the drawstring.

Also, what is the best drawstring material? Is elastic strong enough to pull out that much wet grain? Or do I need some stronger cord?

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Post by BobBrews » 6 years ago

Josh,
Get some polyester cord from the same place you get the voil. The stuff I use is cheap and strong enough to hold all the grain I can lift. Elastic sounds good to hold it around the pot but is not practical. I just use a bungee cord around the bag to hold it in place. see it here....
http://www.stempski.com/biab.php
Last edited by BobBrews on 25 Jul 2011, 21:33, edited 5 times in total.
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Post by Josh » 6 years ago

BobBrews wrote:Josh,
Get some polyester cord from the same place you get the voil. The stuff I use is cheap and strong enough to hold all the grain I can lift. Elastic sounds good to hold it around the pot but is not practical. I just use a bungee cord around the bag to hold it in place. see it here....
http://www.stempski.com/biab.php
Thanks Bob. The design of my bag sounds okay then?
Last edited by Josh on 25 Jul 2011, 21:46, edited 5 times in total.

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Post by BobBrews » 6 years ago

You should be fine! My wife made mine flat not tapered. She did round the corners so the the grain didn't hide there. My bag does drain at the edges and that is a small problem. I am still using that first bag. I know that my brew bag is not up to BIAB standards but it works. This is one of the reasons I love BIAB and brewing in general. As long as your beer turns out OK any method is acceptable. Men are especially able to concoct crazy ways to do anything just to be silly! If I could build a brew kettle out of used beer cans I would do it just to be the only one who has one. There is no wrong way to brew beer.
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