Gum blanket 2.0

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kard133

Full Member
Mar 20, 2010
671
55
Bristol
After seeing CoalCracker Bushcraft on YouTube using an American Civil War item called a Gum Blanket, which is a simple canvas sheet with a vulcanised rubber coating on one side, I thought to myself, that would make the idea groundsheet. It would be spark resistant, more abrasion resistant and quiter than plastic or a space blanket and not in the slightest bit slippy.

The only problem? Getting one from the US at a reasonable cost, they are available from various UK based Cutlers ( suppliers of historical war equipment for reenactors and collectors ) but only with a slit cut in the middle for use as a poncho.

So I researched a DIY route, and various sources cited Flexseal as an altenative to a factory applied rubber coating, however the only sources for this and similar compounds are also quite expensive, usually in the region of £40 and up for enough to coat a decent sized piece of canvas. Then it hit me, I have been using a product called Puraflex 40 to do everything from bonding door panels on the Defender to sealing guttering. According to the manufacturer, "Puraflex 40 is a high modulus, one component, polyurethane hybrid based sealant and adhesive that remains permanently elastic and has good adhesion to most substrates." Polyurethane is commonly used as a synthetic substitute for rubber, and this stuf can be had for approx £5 a tube. It took two tubes to coat the base of the GB 2.0.
IMG_1612.JPG
I tried it on a small piece of scrap canvas, and when it had dried it had the consistancy of, well, rubber. With the waterproof base sorted out, I thought about extra features. So I got a bigger piece of canvas, sewed it into a bag, so it could function as a browse bed, sleeping mat holder or even bivvy bag, and smeared the Puraflex over one side with a spreader knife from poundland, and left it to dry. If I do this again I will cover the uncoated side with paper and masking tape to prevent the smearing you can see in the picture.
IMG_1606.JPGIMG_1607.JPG
Finished weight for this is 1.7Kg (not for ultra lighters) 2m long and 80cm wide. It is completely waterproof on the base, I have had it sitting in the bathtub with tissue paper on the canvas side and a weight for three hours without leakage. It does not slip on the ground, makes no noise and is a tough as nails.

IMG_1610.JPG
IMG_1608.JPG
The thought occurs to me that the Puraflex could be used to re-waterproof the base of 58 Pattern sleeping bags, tents, maybe even old ponchos, however I have not tested it on synthetic fibres. However I do know that it does not bond to polyethylene, like the grabber emergency space blanket, cheap poly tarps or realy cheap tent floors.

Here it is with a roll mat tucked inside, ala cheapskate Savotta FDF sleeping mat.
IMG_1611.JPG
 

Nice65

Full Member
Apr 16, 2009
5,461
1,937
W.Sussex
I reckon you ought to be making a few of those. I’d definitely have one.

My ex army microfibre towel cut down, hemmed, and pop studs fitted to fix to a sheet of waxed cotton canvas was an expensive labour of love. Great as sit mats or to dry the dogs and I’m happy I made a couple, but your invention is brilliant.
 
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After seeing CoalCracker Bushcraft on YouTube using an American Civil War item called a Gum Blanket, which is a simple canvas sheet with a vulcanised rubber coating on one side, I thought to myself, that would make the idea groundsheet. It would be spark resistant, more abrasion resistant and quiter than plastic or a space blanket and not in the slightest bit slippy.

The only problem? Getting one from the US at a reasonable cost, they are available from various UK based Cutlers ( suppliers of historical war equipment for reenactors and collectors ) but only with a slit cut in the middle for use as a poncho.

So I researched a DIY route, and various sources cited Flexseal as an altenative to a factory applied rubber coating, however the only sources for this and similar compounds are also quite expensive, usually in the region of £40 and up for enough to coat a decent sized piece of canvas. Then it hit me, I have been using a product called Puraflex 40 to do everything from bonding door panels on the Defender to sealing guttering. According to the manufacturer, "Puraflex 40 is a high modulus, one component, polyurethane hybrid based sealant and adhesive that remains permanently elastic and has good adhesion to most substrates." Polyurethane is commonly used as a synthetic substitute for rubber, and this stuf can be had for approx £5 a tube. It took two tubes to coat the base of the GB 2.0.
View attachment 69069
I tried it on a small piece of scrap canvas, and when it had dried it had the consistancy of, well, rubber. With the waterproof base sorted out, I thought about extra features. So I got a bigger piece of canvas, sewed it into a bag, so it could function as a browse bed, sleeping mat holder or even bivvy bag, and smeared the Puraflex over one side with a spreader knife from poundland, and left it to dry. If I do this again I will cover the uncoated side with paper and masking tape to prevent the smearing you can see in the picture.
View attachment 69070View attachment 69071
Finished weight for this is 1.7Kg (not for ultra lighters) 2m long and 80cm wide. It is completely waterproof on the base, I have had it sitting in the bathtub with tissue paper on the canvas side and a weight for three hours without leakage. It does not slip on the ground, makes no noise and is a tough as nails.

View attachment 69072
View attachment 69073
The thought occurs to me that the Puraflex could be used to re-waterproof the base of 58 Pattern sleeping bags, tents, maybe even old ponchos, however I have not tested it on synthetic fibres. However I do know that it does not bond to polyethylene, like the grabber emergency space blanket, cheap poly tarps or realy cheap tent floors.

Here it is with a roll mat tucked inside, ala cheapskate Savotta FDF sleeping mat.
View attachment 69074
i just happened to stumble across this tread...
so you basically applied a polyurethane based sealant onto fabric?! i'm rather sure the brand you used isn't available here but maybe something similar exists at a hardware store in this country...
 

Erbswurst

Bushcrafter (boy, I've got a lot to say!)
Mar 5, 2018
3,172
1,262
Berlin
I like old school stuff, no question.

But silent, non slippery and pretty spark resistant are the usual old olive green German army ponchos too. And they serve very well as a ground sheet by the fire. Every German boy scout has one.

The ponchos were even constructed a bit fire retardant. Just for a few seconds of course, until the man can manage to get rid of it if attacked with burning liquids.

Used in usually very good conditions they cost here around 25 €.
I recently bought a couple of 30 years old ponchos and they look like new. But if they are 40 years old they usually are OK as well.

Weight usually between 950 and 1050 g.
Lighter ones are very, very rare. The younger the lighter, month of fabrication stamped inside next to the hood.

1990 / 1991 and younger ones are often nearly unused. Ordered before the reunification and sometimes never issued or just used very rarely because issued together with extra ground sheet, Goretex suits and 30 % polyester - 70 % cotton blend shelter halves (Flecktarn) that also could serve as a rain coat.

The poncho stood a spare option and was mainly meant for protection against biological and chemical attacks and nuclear fall out, stretcher, survival shelter, emergency bivvy bag and spare rain coat.

Dimensions 210 x 160 cm
 
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Very cool! As a former American Civil War reenactor in the US, I can tell you that the Gum Blanket is the most amazing piece of camping gear to come out of the 19th century. I thought about doing a Flex-seal gum blanket but then read that it sticks to itself when you fold or roll the blanket and then doesn't release. I was thinking about trying Plasti Dip instead but haven't gotten around to trying.

After seeing CoalCracker Bushcraft on YouTube using an American Civil War item called a Gum Blanket, which is a simple canvas sheet with a vulcanised rubber coating on one side, I thought to myself, that would make the idea groundsheet. It would be spark resistant, more abrasion resistant and quiter than plastic or a space blanket and not in the slightest bit slippy.
 
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kard133

Full Member
Mar 20, 2010
671
55
Bristol
Interesting! Is Puraflex UV resistant?
The manufacturer doesn't say it is, and a google search on boat forums leads me to believe that UV will break it down over time, however as a ground sheet or lining it should work ok. There are marine grade PU sealants which have high UV resistance according to their spec sheets, such as Puraflex25, but I have not used that one before.
 
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Tony

White bear (Admin)
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Apr 16, 2003
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www.bushcraftuk.com
Cool stuff, I've some ideas that this could work well with, although UV stability would be good. As said, for a bag, groundsheet etc it's an excellent idea.
 
Very cool! As a former American Civil War reenactor in the US, I can tell you that the Gum Blanket is the most amazing piece of camping gear to come out of the 19th century. I thought about doing a Flex-seal gum blanket but then read that it sticks to itself when you fold or roll the blanket and then doesn't release. I was thinking about trying Plasti Dip instead but haven't gotten around to trying.
how did they make the blankets back in the mid 19th century?!
 
All I can say is the Vulcanizing made it possible. I don't fully understand what that is but it involves adding sulfur to natural rubber (latex) which makes it more useful for industrial processes and making products. Goodyear was the fellow who figured it out. During the American CW, many new products were produced using Goodyear's patent, buttons, combs, photograph cases etc.
 

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