Home » Big Book of Leather Chapters » Leather Vessels » When good pitches turn bad…

When good pitches turn bad…

Sometimes when I’m making a leather bottel, particularly if it is for someone younger or I think they might be a little rougher with it, I’ll do a light coat of a bitumen sealer under the pitch. It is cheap, easily applied and stays slightly soft and flexible, helping to keep the bottel sealed if (when) it gets dropped or someone squeezes it and the pitch cracks. The colour shows through the honey-coloured rosin, making it look black the same as real brewer’s pitch.

Costrel 81A5749 from the Mary Rose, 1545.

That’s the theory anyway. I’m making a copy of 81A5749 for a young lady called, appropriately enough, Erin. I’d stitched one end and the top seams and sealed them with one lot of bitumen and then finished the other end. The bitumen was too thick to pour so I took a short trip to the hardware and bought another litre. I sort of noticed this one was a lot runnier than the last lot but didn’t think any more about it. I think they’ve changed the formulation, you can see what happened in the photo below. Looks like I’ll be keeping this for black ones in the future.

"Bum", he said, reaching for the black dye.

This is probably a good time to do a post on the properties of the various sealers that I’ve been planning for some time. I’ll briefly discuss the pros and cons of each of brewer’s pitch and rosin, bitumen sealers and Envriotex. Where I can, I’ll link to the product data and material safety sheets and you can make up your own mind on what to use. Remember to use this information in the context of how often the bottel will be used, and the exposure you will have to the chemicals making it. If you are using the bottel every day, or making a batch of 30, your exposure will be considerably higher than if you only make one or two and only use it a couple of times a year.

Brewer’s Pitch and Rosin

Brewers’ Pitch and rosin are chemically similar. Brewer’s pitch  is rosin extracted from pine wood using a reducing fire, turning it black. Rosin is extracted from the same type of timber using indirect heat so it stays clean rather than picking up soot. The chemical category of these products in this country is “vegetable pitch; brewers’ pitch and similar preparations based on rosin, resin acids or on vegetable pitch” and is similar in the other countries I’ve checked.

Proving that the Internet is a broad church, while this site has some “interesting” ideas, it does have a really good discussion of the various pine-derived pitches. The MSDS is on the same site, I’ve linked to it here.

The advantages of the pitches is that they are thermoplastic, so are soft when hot and harden quickly upon cooling. I can melt a pot and do two or three thin coats in the space of 20 minutes. It reflows, so can be softened with hot water or a cool oven. Minor spills can be scraped off leather without affecting the top coat of wax. They can be brittle if mishandled and do have some fumes when molten that probably best aren’t inhaled, and can cause some horrific burns if you aren’t careful. Considered to contain volatile organic compounds, use is prohibited in parts of the USA.  Pitch can also flavour drinks slightly when new (the same taste as in the Greek wine Retsina) but the flavour is easily removed by leaving your bottel or jack filled with cheap wine overnight. You can’t use pitch with high-alcohol drinks like whisky, or with hot liquids, but it works fine with wine, beer, cider and other cold drinks. As a traditional material, it hasn’t been exposed to as much scrutiny as the more recent materials, the best health advice I could find is “Probably not toxic.” Given that rosin is used as a food additive, I think it’s pretty safe for occasional use.

Bitumen-based paints

Bitumen is an organic hydrocarbon creating by decomposing organic materials, particularly pines, under pressure over a period of tens of thousands of years (or if you own the Great Flood website, somewhere around 4,000). As such, it is chemically similar to  the pitches discussed above. The commercial ones are often thinned with turpentine to a standardised viscosity. This is really a modern take on Stockholm Tar, which is black pine pitch thinned with gum turpentine. Once the turps has evaporated, they are generally approved for use on roofs and tanks containing drinking water. Bitumen has a longer pedigree than pitch, although sealing leather vessels may not be a perfectly accurate use.

As an evaporative drying process, it doesn’t carry the same risk of burns and the hot-melt pitches but otherwise has the same advantages, disadvantages and prohibitions as the pitches. It takes a day or two to dry and as I found, can leave stains that affect the appearance of the finished article. As a modern product the marketing and safety materials are more thorough and specific.

Epoxies

This is where it is going to get contentious…

Epoxies are synthetic thermosetting resins which have a wide variety of industrial and domestic uses. The most common one used in leather vessels in EnviroTex.This particular product cures to a thick, glossy coating in about 8 hours at 21°C, and reaches full strength and toughness in about 48 hours. This durable, resilient material requires no polishing to produce a high gloss. Proponents claim it to be food-safe, although this is only when fully cured after 7 days at 21°C. It is theoretically usable with hot and high alcohol liquids, but see the health concerns below. I’ve seen it in a few leather mugs that have cracked and leak, the only option is to remove it completely and recoat.

The price in Sydney is four times the cost of an equivalent amount of the brushable bitumen sealer. The primary health risk associated with epoxy use is sensitisation to the hardener, which accumulates over time, and can induce an allergic reaction and asthma in sensitive people. Like me. And when I say “over time”, it took me a week of once-daily exposure to glycols and DMPS to become sensitised.

Now the interesting bit. Bisphenol A, which is makes up 85% by weight of EnviroTex, is a known endocrine disruptor. The use of BPA containing chemicals is banned in any reusable food or beverage container in the state of Connecticut, and Maine will have the same ban in place from 2012. On March 29, 2010, the US EPA declared BPA a “chemical of concern”. Much of Europe and Australia have no concern as long as the compounds are used as intended. This specifically excludes the use with heated liquids, where it is known to emit oestrogen-like compounds. Environment Canada listed bisphenol A as a “toxic substance” in September 2010.

The MSDS is here. Given my status as the canary in this coal mine, I won’t use it, but given the number of times you may use it, you may find it appropriate.

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25 thoughts on “When good pitches turn bad…

  1. Thank you. When I receive your e-mail announcements I ask myself “what will I learn today that I did not know I wanted to know”. Well sir you have done it again. Your paints post saved me lost hours on a gorget I made for a local theater group, and this post just rendered useful the hours of research I have spent on finding a “reasonable” sealer for the mugs I am about to make.

    Not sure how you do it, but thank you for sharing. Immensely appreciated!

    John

    • Very few, it is getting hard to get here (mainly due to increased regulation following a couple of “incidents” with alternative medicines) and it melts and is no longer watertight in Summer when you need it most.

      • I probably should elaborate, according to the MSDS, bees wax is not known to be toxic. There was an incident in Australia a couple of years ago when some people had an anaphalactic reaction to a Royal Jelly remedy that had some contaminants. Since then the commercial apiarists have been very reluctant to sell bees wax to the general public as they fear their insurance won’t cover them if someone eats it, has a reaction and sues them. It’s a reflection on the judicial and political system in Australia that people in power can’t tell bee products apart and aren’t interested in finding out. I buy mine from mates but it’s getting difficult to get a good supply.

        It melts at 65 degrees C which is easily achievable in a car or even a tent, and is soft at 35-40 (normal summer day) at which point it slumps and falls off. It also gets brittle in the cold, we often get -6 C on our camping weekends in winter.

        It is regarded as a Dangerous Good by OHS Australia.

  2. Well that is interesting. It’s certainly not a problem to obtain here in the U.S., but then again, our food regulations also permit the coating of fruit with petroleum-based waxes, so perhaps that’s not saying much…

  3. One thing I stumbled on a while back was to use a combination of brewer’s pitch and bees wax (50-50 to 70-30) to get a compromise that would reduce brittleness at low temps, and reduce flow at higher temps. It was from a dubious source and have yet to try it, though I do have the blocks of wax and the brewer’s pitch chips.Have you tried it?

    I had just read up on bitumen for water tank lining before your posts and saw that it was a very popular lining for water tanks and for cisterns (potable water) here in the states for almost a hundred years, and then fell out of favor. And have been stymied in terms of finding appropriate paints, though the sealers came in some pretty amazing colors. Trying to figure out if they are the same thing.

    Do you have a brand name you can share without getting yourself in trouble?

    Regards,

    John

    • I think I can get away with it. The one I’ve been using is marketed under a few brand names, the most common is Ormonoid Brushable Waterproofer. It is made locally in Sydney. If you find a sealer, check that it is rated for contact with potable water at any concentration. A lot say safe for spot use in tanks above 4500l/1000gal.

    • Hi,
      Just reading through all the comments and responses. I was wondering did anybody attempt to mix Beeswax and a tree resin. Do you know of any other tree resin which could be used with beeswax on cotton to wrap food in? This would mean the beswax cloth could be used more easily throughout summer and in the fridge. Any suggestions would be greatly appreciated. Thank you.
      Tara

      • Hi Tara,

        The white rosin I use is a pine resin, damar resin and canuba wax are two food-safe options that you make like to look in to.

        I investigated the use of beeswax cloth food wrap a few years ago and could only find one reference, and that was from a company the made and sold them. I’d appreciate if you had any references to the practice.
        Cheers,

        Wayne

  4. Pingback: Mary Rose Costrel 81A5749 « The Reverend's Big Blog of Leather

  5. I would recommend to everyone that they carefully examine the source of their pitch. Today’s current engima is the sourcing of “true” pine pitch, which, based on the research and information from the folks at Colonial Williamsburg (see the Crispin Colloquy, section on “hand wax” for more details) is as you describe, a very black, very sticky substance strongly smelling of campfires. I would like to reinforce your cautionary comments to your readers regarding the website mentioned above – pine pitch is, by no stretch, a modern invention! I especially love the comment stating “If the Ark was coated with black tar it would be very dark inside, especially on the lower levels.” Was he expecting light to shine through the wood and pitch of a properly sealed boat? =)

    As an additional cookie, this quote comes from D.A. Saguto, Master Shoemaker & Bootmaker at W’burg (who I hope forgives me for taking his name in vain =):

    “If the “brewers’ pitch” was the stuff for lining drinking vessels, it’s a petro-chemical base, non-toxic, and not even vaguely related chemically to pine trees like the stuff you want.”

    • Thanks for the comment, Francis. There may be a trans-Atlantic divide in labelling here. The brewer’s pitch I got from the UK is very black, sticky and smells faintly of both wood smoke and pine trees. The stuff I’ve seen from the USA sold as brewer’s pitch has always been rosin, although most of the drinking vessels beople bring back have been lined with EnviroTex. You have to do your homework.

    • I don’t recall seeing that post recently on Crispin’s is it an older one? I have not been able to find any sources for the thermal plastic (petro-chemical) used to line commercial beer casks for brewing. As far as I can tell it went off market in the late 90s and has never returned. You can find through google searches references on many arts and crafts sites that still reference and praise that stuff.

      Most any searches I have done in the last year usually send me here:
      http://jas-townsend.com/product_info.php?products_id=373

      It lacks some of that black sooty campfire appeal, but it sure smells like pine.

      Is this what you mean to be pointing us towards?

  6. A question if I may. Before I found your blog, I had purchased a leather costrel from the UK. This costrel has a white sealant inside, it looks just like parrafin wax. The water in the costrel gets a really sharp nasty taste to it.
    Any ideas on the sealant used? Any ideas on the bad taste? Can you advise as to what I can do to solve the problem of the BAD tasting water?
    Any advice much appreciated.
    Thank you.
    Regards.

    • Hi Keith, no idea what it might be without seeing it. It could be a rosin or a paint, depends on whether it smells faintly of pine or more plasticky.

      My normal way of getting rid of the taste is to get a really cheap and nasty goon-box red, mix it 50/50 with water and put that in to costrel and leave for a day or two. Tip it out on the weeds in the back yard, rinse and repeat, as they say in the classics, until the nasty taste is gone.

      Cheers,

  7. Thank you. I did read your article, but thought I would ask anyway. Never having used sealants I was not sure what it was supposed to look like. I will try the cheap wine.
    Much appreciated.
    Regards, Keith.

  8. Sorry, Rev, I see you suggested Ormonoid although that’s not available in the UK. For my last flask I used a pond sealant resin called G4 which is safe for aquariums. It certainly makes the flask stout and durable.

  9. Thank you for the excellent article! I’m in the US and it would seem that the only asphalt we can get here is driveway sealer. Would pine tar be a possible alternative for the initial coat you were doing with bitumen? I’d be concerned about using something like driveway sealer.

    • I’d use pine tar as a preference instead of bitumen but can’t get it here. Pine tar is usually pitch softened with distilled turpentine, you may need to let some of the liquid evaporate first so you don’t end up with a fail like mine at the top of the article. It needs to be brushable, not really pourable.

  10. Pingback: Food Safe Coatings for Leather Flasks - The Artful Crafter

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