Author Topic: Canvas impregnation with alum (tutorial)  (Read 10737 times)

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Offline Forest Turtle

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Canvas impregnation with alum (tutorial)
« on: May 02, 2012, 05:05:01 AM »
This is traditional tutorial how to make canvas goods waterproof. It fits on everything with high content of cotton (or linen, I think). Tutorial wasn't invented by myself, it's traditional for Czechoslovak scouts, outdoorsmen of old etc. In contrast with modern impregnation sprays this is not protection  for only top surface of canvas but it's soaked through.  Waterproof effect lasts for  say, several rainy days (I mean rain dawn to nightfall), then you have to repeat impregnation process.

Basic brew is 3 litres, for tarps and big items is needed double brew (6 l or more). Please note, solution is a chemical, so keep safety principles. Open window during work, if you can.

For 3 l of solution is needed:

-   10g bicarbonate (baking soda is possible too)
-   21g alum (aluminium potassium sulphate ? I'm not chemist, is it right in English?)
-   350ml vinegar
-   2650ml hot water (not boiling)
-   Classic soap (for washing laundry, no parfum)
-   Rubber gloves
-   Old pot or bowl and large container for canvas soaking

1)   At first, get together bicarbonate with alum in old pot. Chemic reaction starts immediately. Carefully add an vinegar and wait until fizzing stops. Be really carefull and add vinegar in small brews.

2)   Then put the mixture into large container and pour hot water in it. Be aware of steam! Steam can cause chemical burns on your mucous membranes. Get rubber gloves and put dry canvas into solution. You have to really squeeze the canvas, until it's perfectly soaked.

3)   Remove canvas out of solution and squeeze (not wring!!) again to remove most of liquid from it.

4)   Make halfhearted soapy water and rinse canvas in it. Afterwards squeeze liquid off again.

5)   At last, rinse canvas in clear cold water. It removes remains of soap.

6)   Now, get canvas out and let it dry slowly.

7)   Now you have to well iron it, which increase waterproof effect.


If you were successfull, water makes pools and drops on your tarp! ;-)



I hope it was helpful and understandable. If you didn't understand anything, ask me. I'll try to explain.
« Last Edit: May 02, 2012, 06:02:22 AM by Forest Turtle »
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Offline WoodsWoman

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Re: Canvas impregnation with alum (tutorial)
« Reply #1 on: May 02, 2012, 06:47:39 AM »
Thank you very much Forest Turtle!  This looks like something I can do!   

Like I've mentioned before, I have had a canvas bag in mind to do this with.  If it works and I do it right, we have a bigger canvas cover for a boat I'd like to give this a try on.

I appreciate you taking the time to type this one out.

Thanks

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Offline OutdoorEnvy

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Re: Canvas impregnation with alum (tutorial)
« Reply #2 on: May 02, 2012, 11:21:10 AM »
Very cool post.  Thanks for the info
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Offline MATT CHAOS

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Re: Canvas impregnation with alum (tutorial)
« Reply #3 on: May 02, 2012, 02:18:05 PM »
If I can get all of the ingredients, I am going to try this.  Thanks!
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Offline PetrifiedWood

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Re: Canvas impregnation with alum (tutorial)
« Reply #4 on: May 03, 2012, 07:03:48 AM »
That is neat how the water just beads up on the surface! Thanks for the post.

Offline MnSportsman

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Re: Canvas impregnation with alum (tutorial)
« Reply #5 on: May 03, 2012, 07:24:21 AM »
Thank you Forest Turtle!
:thumbsup:


Very good tutorial!
:)
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Offline easy_rider75

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Re: Canvas impregnation with alum (tutorial)
« Reply #6 on: May 04, 2012, 09:16:30 PM »
Very cool now wondering if this would work for my Finn gas mask bag
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Offline Red

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Re: Canvas impregnation with alum (tutorial)
« Reply #7 on: May 08, 2012, 09:54:22 PM »
this is a fantastic tutorial, thanks very much for sharing with us!
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Offline Barbarossa Bushman

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Re: Canvas impregnation with alum (tutorial)
« Reply #8 on: July 01, 2012, 01:45:31 PM »
I finally read this one. This is great and thanks for the recipe.
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Offline Old Philosopher

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Re: Canvas impregnation with alum (tutorial)
« Reply #9 on: July 02, 2012, 07:50:39 PM »
I just got to this tread, too. Apologies, Forest Turtle!

This is traditional tutorial how to make canvas goods waterproof. It fits on everything with high content of cotton (or linen, I think).
Canvas, cotton, linen...Okay! I'm going to try this on a pair of Levi's and see if I can make emergency rain pants.

For anyone like me who is metrically challenged, I did a conversion.....

For 3 liters of solution:


0.352736 oz bicarbonate of soda (2 slightly rounded tsp)
0.7407456 oz alum (1 1/2 Tbs)
1.479363 cu vinegar (1 1/2 cu)
2.800224 qt water (2qt + 3 1/4 cu)


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Offline acara

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Re: Canvas impregnation with alum (tutorial)
« Reply #10 on: July 03, 2012, 04:24:43 AM »
Thank you.

Quick question..... how does the treatment affect the rigidity of the canvas?

Some of the waterproof techniques (like hand-rub waxing) that I've seen make the canvas rigid, hard to fold....and/or crack when folded tight/taunt.

Also, does the coating make it more susceptible to sparks/embers, or is it about the same (or unknown)?

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Offline Forest Turtle

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Re: Canvas impregnation with alum (tutorial)
« Reply #11 on: July 03, 2012, 05:44:05 AM »
Treatment doesn't make canvas rigid or hard to fold. It is as the same as before waterproofing process, maybe little softer. Treatment soaks into canvas threads, so there is no layer to crack or something.

No, I don't expect any combustibility increase of waterproofed canvas. I've never heard about any case of burned tarp because of alum solution.
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Offline Old Philosopher

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Re: Canvas impregnation with alum (tutorial)
« Reply #12 on: July 03, 2012, 09:09:31 AM »
Interesting process/formula. It would appear the chemicals cause the fibers to swell, making the fabric less porous. That would also account for it seeming to be softer than before.

None of the ingredients are flammable, unlike paraffin, or other petroleum products.
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Offline xj35s

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Re: Canvas impregnation with alum (tutorial)
« Reply #13 on: July 03, 2012, 09:52:14 AM »
alum the same as in the isle with herbs at the grocery store? This sounds way simple if I have the ingredients right...
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Offline Old Philosopher

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Re: Canvas impregnation with alum (tutorial)
« Reply #14 on: July 03, 2012, 10:18:12 AM »
alum the same as in the isle with herbs at the grocery store? This sounds way simple if I have the ingredients right...
From what I can find, basically 'yes'.
FT called it aluminium potassium sulphate. Chemically, it's hydrated potassium aluminium sulfate (potassium alum) with the formula KAl(SO4)2?12H2O.

The food-grade stuff on the spice shelf is more highly refined than the industrial stuff.

As to the question of making the fabric flammable, alum is actually USED AS A FLAME RETARDANT for treating fabrics (like children's pajamas, etc.)
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Offline Forest Turtle

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Re: Canvas impregnation with alum (tutorial)
« Reply #15 on: July 03, 2012, 11:12:20 AM »
Alum as I called it is the same as that stuff used to stop bleeding if man cut himself while shaving with straight razor. Well, I hope it is the same thing in English.
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Offline Old Philosopher

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Re: Canvas impregnation with alum (tutorial)
« Reply #16 on: July 03, 2012, 11:30:16 AM »
Alum as I called it is the same as that stuff used to stop bleeding if man cut himself while shaving with straight razor. Well, I hope it is the same thing in English.
Yep, same stuff. I've used it as a septic for shaving nicks for years. Cook with it, too. Now I know how to waterproof with it. Thanks, FT!
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Offline Forest Turtle

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Re: Canvas impregnation with alum (tutorial)
« Reply #17 on: July 03, 2012, 12:11:40 PM »
Yep, same stuff. I've used it as a septic for shaving nicks for years. Cook with it, too. Now I know how to waterproof with it. Thanks, FT!

You're welcome!
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Offline wolfy

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Re: Canvas impregnation with alum (tutorial)
« Reply #18 on: July 03, 2012, 12:15:36 PM »
The alum method works very well.  I found that recipe years ago in Boy's Life magazine when I was in Boy Scouts.  I used it to waterproof one of mom's old bedsheets that she gave me for use as a tarp.  It shed water well, but the sheet was old and didn't last long.  I'd kind of forgotten about it, so thanks for the reminder :)
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Offline acara

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Re: Canvas impregnation with alum (tutorial)
« Reply #19 on: July 04, 2012, 09:22:09 AM »
Thank you
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Offline WI_Woodsman

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Re: Canvas impregnation with alum (tutorial)
« Reply #20 on: March 29, 2013, 05:46:01 PM »
Fascinating!  I seems more breathable than waxed/oiled canvas!  I'm going to use this process on one of my anoraks! 

Offline wsdstan

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Re: Canvas impregnation with alum (tutorial)
« Reply #21 on: March 29, 2013, 06:23:13 PM »
Thank you Forest Turtle, good presentation.  I will try it on my coveralls and my old canvas Eureka tent.

Old Phil, thanks for the conversions........ I am quite challenged with the metric system so it helps.
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Offline OffGrid9

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Re: Canvas impregnation with alum (tutorial)
« Reply #22 on: September 20, 2017, 05:38:49 PM »
This is an old thread, but I wanted to add to the discussion.  If no one responds, I'll consider starting a new topic.

I read with interest the tutorial posted by Forest Turtle.  The process he described for waterproofing canvas may be a more effective technique than the one I am going to post.  I copied it from the original bush-lore book, Woodcraft, written by Nessmuk (pen-name of George Washington Sears) back in the early 1880's, published in 1884, and still in print.  It's WAY old-fashioned...it's 133 years old, and he was no spring chicken when he wrote it, so likely it was old-fashioned when it was published.  It's a bit hard to read, with many dated terms -- some so obscure that I never figured out what they meant.  But that old man really knew his stuff.  He lived it for so many years.  My dad was given the book by HIS dad when he was a kid, and he treasured it...gave it to me 63 years ago when I was 10.  I loved it then, and still do.  My copy is dog-eared, but still readable.  I hope my grand-kids will take the time to read it.  If they do, they'll treasure it, too.

Nessmuk described a simple process for waterproofing any cotton material, from muslim to denim to canvas.  i'm pretty sure it would work on other natural-fiber material, such as linen (flax).  I don't believe it will work on man-made fibers, but we never tried that.  In 1957 or 58, my dad used it to waterproof a tent and two light cotton rainbreaker jackets for us, and it worked well.  The fabric stayed supple.  It seemed to last a long time...a couple of years as I recall, maybe more.

Anyway, here's Nessmuk's recipe:
     "The cloth does...need a little waterproofing:  for which the following receipt [recipe] will answer very well, and add little or nothing to the weight:  To 10 quarts of water add 10 ounces of lime, and 4 ounces of alum;  let it stand until clear;  fold the cloth...and put it in another vessel, pour the solution on it, let it soak for 12 hours;  then rinse in luke-warm rain water, stretch and dry in the sun...".  Woodcraft, p. 31

There are a lot of different chemical compounds known as alum, but Dad figured the most common and available in Nessmuk's day was potash alum (aluminum potassium sulfate), so that's what he used.  There are also three or more types of lime...but since Nessmuk didn't specify (and because he was a woodsman and trekker, not a chemist), Dad figured he'd have used common powdered agricultural lime (mostly calcium carbonate).  Dad made a triple-batch, wound up with almost eight gallons...even a small tent takes a lot of liquid to immerse it.  Following Nessmuk's "receipt", he added the lime and alum to the water and let it stand...but the lime didn't dissolve.  After stirring and waiting, the liquid did settle and clear, with some lime on the bottom.  Absent any other direction, Dad just stirred it up and poured all of it over the canvas items in a plastic kiddie-pool.  He let them soak for more time than directed (about 24 hours, I think), then rinsed all the items in clean, SOFT, well water (not having any rainwater handy).  After he'd rinsed them enough to remove any residual lime, we dried everything in the yard (we erected the tent, hung the jackets).

And like I said, it worked.  It may not have worked as well as Scotchguard, but the modern water-repellents weren't available in 1957.  And now 3M says it will stop producing Scotchguard because it's not environmentally friendly.  So maybe the old ways will stage a come-back -- old Nessmuk rides again!
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Offline wolfy

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Re: Canvas impregnation with alum (tutorial)
« Reply #23 on: September 20, 2017, 06:07:23 PM »
 :welcome: to the B&B forum, OG9!   I see by your profile page that you're from Washington state..... a better place to test a waterproofing-agent does not immediately come to mind! :lol:   Great 1st post, BTW, but why don't you run over to 'INTRODUCTIONS' and tell us a little about yourself and your interests.....nice to have you aboard. :cheers:
« Last Edit: September 20, 2017, 08:12:07 PM by wolfy »
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Offline OffGrid9

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Re: Canvas impregnation with alum (tutorial)
« Reply #24 on: September 20, 2017, 07:29:47 PM »
Thanks for the welcome, Wolfy.  I was actually writing my autobiography in the intro board as you were posting your message.  It's sort of a novella.  Never did learn when to stop....
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Offline buzzacott

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Re: Canvas impregnation with alum (tutorial)
« Reply #25 on: September 23, 2017, 12:34:09 AM »
Awesome thread.

And welcome OffGrid9
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Offline 1066vik

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Re: Canvas impregnation with alum (tutorial)
« Reply #26 on: September 23, 2017, 09:22:59 AM »
thanks for resurrecting this thread!
I need to try this out -- and have some grocery grade alum I can play with along with washing soda.

how well does this hold up to the temperate rainforest in your part of the woods?

Offline OffGrid9

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Re: Canvas impregnation with alum (tutorial)
« Reply #27 on: September 24, 2017, 11:52:04 AM »
thanks for resurrecting this thread!
I need to try this out -- and have some grocery grade alum I can play with along with washing soda.

how well does this hold up to the temperate rainforest in your part of the woods?

...I'm embarrassed to say I don't know how well it would hold up to Washington state's wet weather.

My dad decided to resurrect old Nessmuk's process back in 1957, mainly because Scotchguard wasn't yet on the market (or if it was, we didn't know about it).  We had a nice old two-man tent of light canvas, but if it had ever been water-resistant, it had lost that feature over time.  We also had a couple of nice windbreakers of light, tightly woven cotton material...probably heavy cotton drill, but maybe light canvas, and they too wouldn't shed even a light rain.  Dad and I had both read Woodcraft, and we remembered the advice about making fabric rain-proof.  So we followed the book's directions as well as we could, and it worked.

I don't remember ever testing the tent or jackets in a heavy downpour, but we stayed dry in that tent for at least a couple of years of summer/fall camping in the Blue Ridge mountains, some nights in light rain.  I lost my jacket when I left Virginia in 1961.  At some point I'd started using Scotchguard -- I just can't remember how long the alum/lime process kept the fabric water-resistant.
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