Should I Make a Bag or Can I Buy One? 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.
Bags Designed by BIABrewer BIABrewer has designed a bag that is tapered, elasticised, tabbed and designed to suit 40-100lt pots. It is quite complex and therefore expensive and time-consuming to make as a one-off item. As BIAB grows, BIABrewer, will look at finding a source of affordable bags to supply retailers. Until then, the bag specifications and use thereof have been provided free of charge to Gryphon Brewing (BIABrewer’s local retailer.)
If you are unable to purchase one, let’s have a look at how to make a perfectly adequate bag...
Material The best material to make your bag from is sometimes known as “Swiss Voile.†This is a 100% polyester curtain sheer. It is a fine mesh, a lot finer than fly screen for your windows but not as fine as muslin cloth. If women’s stockings were the right shape and size, their porosity would probably be perfect! For instance, if you filled it up with flour and shook it, the flour would come through, but nothing else would. Water would fall through it without resistance.
So, if you are making your own bag, go for an un-dyed (e.g. white or ivory) polyester material that approaches the above description and you won’t go wrong.
Size Size does matter! Your bag must be BIG enough to line your pot completely and without restricting the grain in any way. In BIAB you are not mashing “in a bag†you are mashing in a pot that just happens to be lined with a bag.
A fail-safe rule of thumb is that you need to be able to fit your pot inside the bag.
Design/Shape The ideal BIAB bag shape is tapered, difficult to sew and hard to describe but simple shapes and designs such as pictured below work perfectly well. (Forget the carry straps though!)
(You might have to click on the above image to see the third shape properly.)
The third shape is very simple to make and works extremely well. It is based on a tapered pillow slip shape. All that needs to be done is to cut two pieces of material in the shape above and sew them together. 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 (1â€) for drawstring or elastic.
base = kettle base diameter – 15%
A drawstring or elastic and tabs, hold the bag securely and allow lifting out of the kettle.
Stitching Make sure all your stitching uses polyester thread. Use over-locking, or another form of strong stitch to sew your bag. Check the stitching regularly on your first few brews. The right material with strong stitching should give you a bag of indefinite life.
There you go!
I'm not as think as you drunk I am.