Well, Plataea 2022 ended on Saturday and although there's a lot to be said, I'm limiting myself to some observations to bear in mind about all the stuff I brought out there:
- A four-inch-wide (internal), eight-foot-long PVC pipe with caps held on by duct tape makes a very protective package for spears, but it's so heavy and awkward (particularly when you already have two suitcases and a rifle case with your bows and arrows in it), and expensive to ship, that I wound up leaving both it and all my spears spears with other reenactors who felt they'd have a use for them and less difficulty/expense transporting them. I will not travel with spears in the future. If I send any more to Greece, I'll send them well ahead of time by the cheapest service available and leave them with a trusted friend.
- Under the (to my Pennsylvanian standards) quite aggressive heat and sun, the film of linseed oil-beeswax sealer I applied on top of the oil paint on my crescent shield softened and rubbed off. Specifically, the area on top of the dark red ochre-painted part of the shield; the area on top of the white edge was somewhat more resistant (presumably because the film is transparent and the dark paint heated up in the sun faster). The same mixture used as a paint binder on my new gorytos was also more resistant, but did soften after prolonged exposure, allowing thicker bits to be scraped off. The rosin-beeswax glue attaching the leather facing of my new akinakes scabbard also softened. By contrast, anything treated, bound or sealed with only linseed oil or rosin (the ochre paint on the shield, the spear handles, and the sinew wrappings of my arrows) were all fine. So basically anything containing beeswax was in danger of melting.
- The buff leather weapon belt performed admirably. The chrome-tanned belt sagged and became uncomfortable. I'm not sure whether this is because the holes I punched in the buff belt allowed it to be laced tighter or because it's a thicker leather, but I suspect both. The belt being nice and snug was definitely helpful.
- As I suspected, the smaller bow and commensurately smaller gorytos and arrows were much easier to carry. The search for an accurately Classical-styled bow of less than 36 inches strung continues.
- The 1/2-inch-thick wooden crescent shield is at least as heavy as larger wicker ones in the same style. This, too, needs improvement. I also threw together a round wicker mat with pelta-style grips and a suede facing, which at 16 inches in diameter (about the size of the smallest Scottish targes, and barely large enough to cover my arm from elbow to knuckles with fingers closed around the handgrip) is so light I barely notice I'm wearing it, but I'd have felt much, much better about it if it were crescent-shaped.
- A 12-ounce ceramic bottle, while convenient to carry, is only around a quarter as much water as I need to drink over the course of a Greek midsummer day in the field. Also, water left out becomes as hot as the surrounding air in just a few hours. What I wound up doing was to take a two-liter plastic bottle of water and keep it overnight in the hotel minifridge where it half-froze, wrapped it in spare clothing and kept it in my tent in my suitcase. That way I could still at least refill my ceramic bottle with slightly cool water by the end of the day. A proper cooler with ice blocks would've been better.
- Food must be kept elevated or it will be invaded by ants. A table of some kind, a crate, a box, anything will help.
Showing posts with label paint. Show all posts
Showing posts with label paint. Show all posts
Wednesday, August 3, 2022
Various practical addenda from Plataea 2022
Thursday, April 2, 2020
Painted suede is a conditional go
About a year and a half ago, Todd Feinman at RAT told me about a period leather finish that could be made from one part melted beeswax and two parts linseed oil. The oil polymerizes so that the mixture isn't sticky when cured, and the beeswax keeps the mixture flexible.
Regular readers will recall that I've long been troubled by the question of how to reproduce the crenelated decorations frequently seen on Greek depictions of the gorytos. You could stitch on dyed leather or cloth, but that always struck me as needlessly laborious, and very difficult unless the case's main seam were opened up, so I've concentrated on finding a paint that will do the trick. It's my understanding that the gorytos and other such gear were made from soft, sueded leather cured with fat or oil, similar to braintan, so any paint would need to be water-resistant (as braintan-type leather soaks up water like a sponge and is hard to seal) and flexible so as not to flake off. It recently occurred to me that the beeswax-oil sealer might make a good paint binder for that purpose.
I tried it out by mixing a little melted sealer and red ochre (I didn't take measurements, but the amount of ochre wasn't enough to thicken the binder significantly), and when it cooled, rubbing it into a scrap of buckskin, scraping off the excess, and rubbing what was left in again. A few days later, when it felt dry, I cut the scrap in half and rubbed a top coat of unpigmented sealer onto one of the pieces. I also tried "priming" another scrap with sealer before painting it and adding a top coat, and rubbing/scraping/rubbing plain red ochre oil paint onto a third piece, which was also then given a top coat.
Yesterday I put all four pieces into a sink full of water and let them soak for an hour and a half. The result was impressive: None of the paint on any of the four pieces ran, smeared, or softened in water. They had apparently sealed in all the pigment in a good-as-waterproof manner. I even scraped the paints with my fingernail and none came off. The plain oil paint worked just as well when rubbed and scraped instead of merely brushed on, but it cured much stiffer than the beeswax-oil paint, so between the two, I think the beeswax is preferable. The additional top coat was not needed, though I suspect it would make the paint job more durable in the long run. Because German buckskin is so pale, only a little paint is needed.
This technique comes with a number of caveats:
1. I know of no evidence whatsoever that the Persians or anybody else actually used a paint like this in antiquity. The materials would've been available, but I have no reason to think that anyone combined them and used them in this manner, other than that it would've been a great way of making those crenelated bowcase decorations.
2. I used hardware-store boiled linseed oil. This version has some sort of chemical additives that cause it to cure faster than the kind that would've been available in our period, which (if used as a paint binder) would've been functionally equivalent to the purer linseed oil still sold in art stores for making traditional oil paint. In other words, if you use the more period-correct oil, you'll need to allow much more time for it to "dry." On the other hand, it's doubtlessly less toxic.
3. Many leatherworkers believe that linseed oil's chemical properties degrade leather fibers over time. However, I think the paint only soaks in shallowly, so I don't think it'll prove much of a problem.
4. The rubbing and scraping technique is useful only for producing large, simple designs. It may be possible to apply finer oil paint designs on leather that's been glued to a hard surface and primed with drying oil; if so, that technique might be appropriate for scabbard facings glued to a wood core.
Regular readers will recall that I've long been troubled by the question of how to reproduce the crenelated decorations frequently seen on Greek depictions of the gorytos. You could stitch on dyed leather or cloth, but that always struck me as needlessly laborious, and very difficult unless the case's main seam were opened up, so I've concentrated on finding a paint that will do the trick. It's my understanding that the gorytos and other such gear were made from soft, sueded leather cured with fat or oil, similar to braintan, so any paint would need to be water-resistant (as braintan-type leather soaks up water like a sponge and is hard to seal) and flexible so as not to flake off. It recently occurred to me that the beeswax-oil sealer might make a good paint binder for that purpose.
I tried it out by mixing a little melted sealer and red ochre (I didn't take measurements, but the amount of ochre wasn't enough to thicken the binder significantly), and when it cooled, rubbing it into a scrap of buckskin, scraping off the excess, and rubbing what was left in again. A few days later, when it felt dry, I cut the scrap in half and rubbed a top coat of unpigmented sealer onto one of the pieces. I also tried "priming" another scrap with sealer before painting it and adding a top coat, and rubbing/scraping/rubbing plain red ochre oil paint onto a third piece, which was also then given a top coat.
Yesterday I put all four pieces into a sink full of water and let them soak for an hour and a half. The result was impressive: None of the paint on any of the four pieces ran, smeared, or softened in water. They had apparently sealed in all the pigment in a good-as-waterproof manner. I even scraped the paints with my fingernail and none came off. The plain oil paint worked just as well when rubbed and scraped instead of merely brushed on, but it cured much stiffer than the beeswax-oil paint, so between the two, I think the beeswax is preferable. The additional top coat was not needed, though I suspect it would make the paint job more durable in the long run. Because German buckskin is so pale, only a little paint is needed.
This technique comes with a number of caveats:
1. I know of no evidence whatsoever that the Persians or anybody else actually used a paint like this in antiquity. The materials would've been available, but I have no reason to think that anyone combined them and used them in this manner, other than that it would've been a great way of making those crenelated bowcase decorations.
2. I used hardware-store boiled linseed oil. This version has some sort of chemical additives that cause it to cure faster than the kind that would've been available in our period, which (if used as a paint binder) would've been functionally equivalent to the purer linseed oil still sold in art stores for making traditional oil paint. In other words, if you use the more period-correct oil, you'll need to allow much more time for it to "dry." On the other hand, it's doubtlessly less toxic.
3. Many leatherworkers believe that linseed oil's chemical properties degrade leather fibers over time. However, I think the paint only soaks in shallowly, so I don't think it'll prove much of a problem.
4. The rubbing and scraping technique is useful only for producing large, simple designs. It may be possible to apply finer oil paint designs on leather that's been glued to a hard surface and primed with drying oil; if so, that technique might be appropriate for scabbard facings glued to a wood core.
Friday, December 21, 2018
Testing casein paint on leather, part III
Dammit.
Our test board cured for an entire month. Last week I added some thin layers of carnauba wax paste, which is, admittedly, not something that would've been available at the time (carnauba palms are native to Brazil), but I was attracted to the fact that it's harder than beeswax and has a higher melting point. It's difficult to see, but on some of the swatches it dried to a whitish waxy appearance. At this point, my favorite was the glue-soaked, sanded leather with a wax topcoat and no gesso (lower right corner), which was smooth and a bit glossy.
I wanted to first test the paint against rough surfaces and sharp implements to see if it would flake. It didn't, though the knife and half brick scuffed the paint applied over unglued leather badly. The glued/sanded/waxed/un-gessoed swatch looked to be the most durable, as both implements glided over it leaving superficial scratches.
The real test, of course, would be the rain. I waited until today when it was convenient to set the board outside for an hour, as I figure these are realistic conditions.
In the meantime, I cut up a whole bunch of undyed, semi-bleached linen swatches, as I figure these would be the most likely to show paint smudges if someone's clothing were to come into contact with wet paint. When the board came inside, I rubbed one swatch of linen against each swatch of paint.
At this point, it became difficult to read the labels, but that didn't matter. NONE of the paint swatches adhered well enough for practical use; each one smudged badly onto the linen.
Sadly, the glue-soaked but un-gessoed swatches fared by far the worst, as the glue absorbed water and turned liquid. The paint slid right off of them. The gessoed ones didn't do much better. The wax topcoats gave no noticeable protection. In fact, the leather swatch with no treatment at all (corresponding to the linen at the bottom of the leftmost column) did best - or, at least, least worst - although as you can see, it still smudged.
So where do we go from here?
The thing is that milk paint is normally applied to raw wood, and it's said to be durable in this application, particularly if coated with a drying oil. This leaves us with several options:
1) Bare wood scabbards with only a drying oil or wax finish.
2) Painted wood, again probably having a water-resistant finish.
3) Unpainted leather facings, perhaps vat-dyed in a single color (I am told that a finish of beeswax and drying oil will prevent dye bleeding, but that's a question for another day).
4) Embossed sheet metal facings, either over a leather facing or glued directly to the wood.
5) Oil paint or encaustic (wax). Unfortunately, I know of no evidence that these types were used in our period.
The first two leave us with the issue of the scabbard possibly splitting along the seams when the blade is pushed in or jostles inside the scabbard while the wearer is running. Only the chape would provide reinforcement. It's possible that small bands of organic material such as rawhide were tied or stitched around the scabbard farther up, leaving most of the wood bare for painting, but that's pure speculation.
Options 3 and 4 have good historical grounding, as the Issyk Golden Man's scabbard was covered largely with leather and small sheet gold adornments, while the Achaemenid scabbard from Egypt had a (now-vanished) gold facing pasted to the wood. We're still left between a rock and a hard place: Most reenactors won't have the skills, or money to pay someone who does have the skills, to make a full metal facing, since fitting one to the complex curves of a wooden core in the classic Achaemenid shape would require lots of careful hammering to expand the metal in certain areas. On the other hand, leather alone is pretty dull-looking, and I've never seen evidence for Achaemenid scabbards with partial metal plates such as those at Issyk which would be easier to make.
I'll look into carrying out milk paint tests directly on wood. In the meantime, Ivor at RAT brought to my attention the book Chariots in Ancient Egypt, which is said to have some evidence for painted leather. Now I have a few more weeks of free time before the spring semester starts, I can finally start checking whether it contains anything potentially applicable to our situation.
Sadly, the glue-soaked but un-gessoed swatches fared by far the worst, as the glue absorbed water and turned liquid. The paint slid right off of them. The gessoed ones didn't do much better. The wax topcoats gave no noticeable protection. In fact, the leather swatch with no treatment at all (corresponding to the linen at the bottom of the leftmost column) did best - or, at least, least worst - although as you can see, it still smudged.
So where do we go from here?
The thing is that milk paint is normally applied to raw wood, and it's said to be durable in this application, particularly if coated with a drying oil. This leaves us with several options:
1) Bare wood scabbards with only a drying oil or wax finish.
2) Painted wood, again probably having a water-resistant finish.
3) Unpainted leather facings, perhaps vat-dyed in a single color (I am told that a finish of beeswax and drying oil will prevent dye bleeding, but that's a question for another day).
4) Embossed sheet metal facings, either over a leather facing or glued directly to the wood.
5) Oil paint or encaustic (wax). Unfortunately, I know of no evidence that these types were used in our period.
The first two leave us with the issue of the scabbard possibly splitting along the seams when the blade is pushed in or jostles inside the scabbard while the wearer is running. Only the chape would provide reinforcement. It's possible that small bands of organic material such as rawhide were tied or stitched around the scabbard farther up, leaving most of the wood bare for painting, but that's pure speculation.
Options 3 and 4 have good historical grounding, as the Issyk Golden Man's scabbard was covered largely with leather and small sheet gold adornments, while the Achaemenid scabbard from Egypt had a (now-vanished) gold facing pasted to the wood. We're still left between a rock and a hard place: Most reenactors won't have the skills, or money to pay someone who does have the skills, to make a full metal facing, since fitting one to the complex curves of a wooden core in the classic Achaemenid shape would require lots of careful hammering to expand the metal in certain areas. On the other hand, leather alone is pretty dull-looking, and I've never seen evidence for Achaemenid scabbards with partial metal plates such as those at Issyk which would be easier to make.
I'll look into carrying out milk paint tests directly on wood. In the meantime, Ivor at RAT brought to my attention the book Chariots in Ancient Egypt, which is said to have some evidence for painted leather. Now I have a few more weeks of free time before the spring semester starts, I can finally start checking whether it contains anything potentially applicable to our situation.
Friday, November 16, 2018
Testing casein paint on leather, part II
Saturday, October 13, 2018
Background for testing casein paint on leather
Casein paint, or milk paint, is made by mixing milk protein (usually concentrated or coagulated) with pigment and often hydrated lime, which causes a chemical reaction that makes the dried paint harder and more durable. Roman reenactors frequently use it to paint their scuta (large legionary shields) and report that it's fairly water-resistant, more so if a wax top coat is applied. The basic ingredients should have been available in Achaemenid Persia, and the use of milk paint is documented from the Bronze Age, so I consider it a reasonable option for period-appropriate paint.
Could it have been used on tanned leather? I'm planning to make some more akinakes scabbards - well, sort of; I'll have to farm the wooden cores out to a professional woodcarver this time because I no longer have access to the kind of tools that are needed to produce them in a reasonable timeframe. Anyway, wooden scabbards are greatly strengthened with a facing or other reinforcements to keep them from splitting along the seams, but aside from the chape (when it was made as a separate piece), the only reinforcements known on akinakes scabbards are facings and the only facings known are leather and embossed sheet metal. Shaping sheet metal around the expanded throat of an Achaemenid scabbard requires great skill, so I'm going to rule it out. That leaves leather. As I've said before, I believe the usual leathers used in the period were fat-cured (similar to braintan and chamois) or rawhide.
Chamois is cured with fish oil, just like buff leather and German buckskin. In the U.S. it's made from sheepskin, although the term chamois in French refers to a species of goat. As a result, chamois is thin, elastic and soft, so it should be easy to stretch over a scabbard. Its non-abrasive properties make it popular for polishing cars, so it can be bought in automotive and hardware stores. I bought a three-square-foot piece from Ace Hardware for $20; I think this should be sufficient for covering two scabbards.
Milk paint is generally said to need a ground (the surface onto which it's painted) that is both hard and porous. It works very well on raw wood. On vegetable-tanned leather it's sometimes reported to crack. However, as far as I know, nobody's tried it on suede leather before, so I wonder if it might not be able to soak in like thin hide glue paint.
An alternate method might be to harden the leather by soaking it in hide glue. However, I believe this would reduce its porosity. There are two methods of prepping a non-porous surface for being painted with milk paint that I read of: sanding the surface to roughen it and give the paint something to "bite" into, and priming it with gesso, which is a mix of glue and chalk dust.
RAT member Feinman informs me that soaking the leather with hide glue would make it hygroscopic (meaning it would tend to absorb atmospheric humidity), which could present problems for paint adhesion. I know of no way of dealing with this.
The other factor is whether or not to apply wax. Over bare suede, I think that wax would tend not to seal very well.
For the time being, I intend to test everything. I've gotten a wooden plank and attached small swatches of chamois with hide glue, each of which will then have some milk paint applied. There are nine swatches, the three largest of which will be shared by two test treatments, so as to try every combination of leather glued only by the back, soaked with glue, sanded or not, primed with gesso or not, and waxed or not.
(The nailed-down rawhide pieces in the middle were from another project.) As you can see, the glue-soaked chamois is brown and almost transparent. It dries hard enough that I can barely dent it with my thumbnail, although it's not as hard as rawhide. Also, chamois that's glued on the back but not soaked and then allowed to dry can be soaked later by rubbing more glue on the front. The glue seems to bond the chamois pretty strongly to the wood.
Over the next few days I'll have to narrow down the possible choices of gesso and wax. Once all the paints are thoroughly cured (allow a month) and treated, I'll test the paint's adhesion when dry, adhesion when wet, and resistance to bleeding and smearing when wet. Stay tuned!
Could it have been used on tanned leather? I'm planning to make some more akinakes scabbards - well, sort of; I'll have to farm the wooden cores out to a professional woodcarver this time because I no longer have access to the kind of tools that are needed to produce them in a reasonable timeframe. Anyway, wooden scabbards are greatly strengthened with a facing or other reinforcements to keep them from splitting along the seams, but aside from the chape (when it was made as a separate piece), the only reinforcements known on akinakes scabbards are facings and the only facings known are leather and embossed sheet metal. Shaping sheet metal around the expanded throat of an Achaemenid scabbard requires great skill, so I'm going to rule it out. That leaves leather. As I've said before, I believe the usual leathers used in the period were fat-cured (similar to braintan and chamois) or rawhide.
Chamois is cured with fish oil, just like buff leather and German buckskin. In the U.S. it's made from sheepskin, although the term chamois in French refers to a species of goat. As a result, chamois is thin, elastic and soft, so it should be easy to stretch over a scabbard. Its non-abrasive properties make it popular for polishing cars, so it can be bought in automotive and hardware stores. I bought a three-square-foot piece from Ace Hardware for $20; I think this should be sufficient for covering two scabbards.
Milk paint is generally said to need a ground (the surface onto which it's painted) that is both hard and porous. It works very well on raw wood. On vegetable-tanned leather it's sometimes reported to crack. However, as far as I know, nobody's tried it on suede leather before, so I wonder if it might not be able to soak in like thin hide glue paint.
An alternate method might be to harden the leather by soaking it in hide glue. However, I believe this would reduce its porosity. There are two methods of prepping a non-porous surface for being painted with milk paint that I read of: sanding the surface to roughen it and give the paint something to "bite" into, and priming it with gesso, which is a mix of glue and chalk dust.
RAT member Feinman informs me that soaking the leather with hide glue would make it hygroscopic (meaning it would tend to absorb atmospheric humidity), which could present problems for paint adhesion. I know of no way of dealing with this.
The other factor is whether or not to apply wax. Over bare suede, I think that wax would tend not to seal very well.
For the time being, I intend to test everything. I've gotten a wooden plank and attached small swatches of chamois with hide glue, each of which will then have some milk paint applied. There are nine swatches, the three largest of which will be shared by two test treatments, so as to try every combination of leather glued only by the back, soaked with glue, sanded or not, primed with gesso or not, and waxed or not.
Over the next few days I'll have to narrow down the possible choices of gesso and wax. Once all the paints are thoroughly cured (allow a month) and treated, I'll test the paint's adhesion when dry, adhesion when wet, and resistance to bleeding and smearing when wet. Stay tuned!
Sunday, June 8, 2014
Hide glue paint - the rain test!
Clockwise from bottom: acrylic, hide glue with natural pigment, hide glue with natural pigment and food color, hide glue with pigment and alum, and hide glue with pigment, food color and alum.
After an hour's soak and a little rubbing.
Wow! All the hide glue patterns washed out to the point of being barely noticeable, regardless of alum content. Either I'm missing some information, or this is just to be expected - if historical paintwork was done in this way at all.
Thursday, May 29, 2014
Hide glue paint tests - preliminary results
Achaemenid motifs on glove suede painted in acrylic (left), hide glue with added alum (top) and hide glue without added alum (bottom).
In the first batch (without alum), it took a water-glue-pigment ratio of about 5:3:2 to get the consistency I wanted. I am just now realizing that I scaled the mixture down wrong and added twice as much alum to the second batch as I should have, which accounts for why it was somewhat thicker than the first batch (premature gelling - the alum content was probably around 3-4 percent instead of 1-2).
The thick consistency of the second batch - also probably caused by stirring up as much of the pigment as possible, as I noticed the first time that it tended to settle - meant that it didn't soak into the leather as readily, making for a blobby-looking design. Since these test designs are very small, I think in more practical use it won't be much of a problem. You can try different amounts of water and find what you prefer.
The acrylic paint is very slightly glossy, while the hide paint isn't, but I wouldn't say the acrylic looks too bad. As for flexibility, the acrylic is far more flexible, but I think the hide paint has adhered well enough to the suede that it won't flake off.
Another
issue is that the only pigment I had in the house was raw sienna, which
when added to the glue, gave it a color almost identical to the leather
itself - you can only see the faravahar on the top swatch because the
painted areas reflect light differently. This will make the last test hard to judge; I may try again with some food coloring added just to mark clearly where the paint is to begin with. The last test is to soak the swatches and see whether the paints run; this will hopefully show us how our stuff will handle rain. The acrylic paint manufacturer suggests "air-curing" it for one week before cleaning, so I'll be trying this out in a week and will probably report the results on Friday.
Tuesday, May 27, 2014
Hide glue paint tests - gearing up
Thesis
It is possible to paint soft-tanned leather goods using basically period materials.
Background
Animal glue is one of the oldest-known adhesives in the world, second only to plant resins. Archaeological evidence dates back to the Neolithic, written references back to the Bronze Age. It's made by cooking down animal tissues that are high in collagen, a connective protein; these tissues are typically bone, tendon, or particularly skin (strictly, hide glue is only that made from skin). Today it's still widely used by woodworkers, especially those engaged in making and repairing stringed instruments.
Animal glue is also used as a paint sizing, the substance in which the pigments are dissolved and by which they adhere to the canvas. Plains Indians used a thin solution of glue for painting buckskins. It's supposed to soak partly into the hide, remaining semi-flexible - the rough, "open" finish on brain-tan probably helps with the absorption. Since the most common leathers of the ancient Mediterranean were similar to brain-tan, this sounds like a plausible solution for us.
Standard "hot" hide glue must be held at around 140 degrees Fahrenheit while working: colder and it will gel, much hotter and the collagen will begin to break down, weakening it. However, hide glue can be kept liquid at room temperature by the addition of an anti-gelling agent, commonly salt or urea. While I can't prove that it was used historically, urea was always readily at hand in the form of urine. That may sound disgusting, but when you think about some of the things people had to do to make leather, adding pee to glue suddenly doesn't sound that farfetched. Thankfully, we don't have to trouble ourselves with that, because premixed liquid hide glue is already available at some hardware stores.
While liquid hide glue has a lesser reputation than hot hide glue due to the urea weakening its bonding power, and unused portions will break down over time, Stephen Shepherd of Full Chisel has argued that fresh liquid hide glue is still one of the stronger glues available. In any case I'm not sure whether the strength of the glue is as critical in painting as it would be in woodworking.
There is one other consideration: While Greece is pretty dry in the summer, most of our stuff would have been exposed to rain sooner or later in ancient times. Hide glue isn't waterproof by itself, but can be made highly water-resistant by the addition of a small amount of alum. Again I have no reason to think this was done, but alum was used as a mordant and leather tannage, so it was at least available. The containers and brushes used with glue that has alum added, must be washed thoroughly before the paint dries or it will be difficult or impossible to wash out afterward.
Materials and methods
Liquid hide glue
Water for diluting glue
Alum (aluminum sulfate)
Earth pigment
Suede leather scraps
Alum is recommended in amounts of 1-2 percent. Too much can cause the glue to gel prematurely. Assuming it has a similar weight to salt, for one ounce of glue (before dilution), I estimate one twentieth of a teaspoon would be the correct amount, but since it's so hard to measure in such quantities, I'll try it by eye - slightly less than half of an eighth of a teaspoon ought to be close.
In order to mix the alum thoroughly into the glue, it should probably be dissolved in the water first. An exact ratio of water to glue is not given in the Crazy Crow instructional, so I'll begin with a 1:2 ratio which hopefully won't make it too dilute to begin with. Let's start with a tablespoon of glue, a teaspoon and a half of water, and half of a half of an eighth of a teaspoon of alum.
The bottle on the left is a modern acrylic leather paint I have on hand, which I'll be comparing to the hide paint to see whether it's acceptable as a more convenient substitute.
Questions
Does hide paint remain flexible enough when dry for use on soft leather goods (gorytoi, bags, clothing)?
Does waterproofing with alum affect the paint's flexibility?
Does acrylic leather paint provide a similar appearance and degree of flexibility and water-resistance to alum-treated and alum-free hide paints when used on the same leather?
It is possible to paint soft-tanned leather goods using basically period materials.
Background
Animal glue is one of the oldest-known adhesives in the world, second only to plant resins. Archaeological evidence dates back to the Neolithic, written references back to the Bronze Age. It's made by cooking down animal tissues that are high in collagen, a connective protein; these tissues are typically bone, tendon, or particularly skin (strictly, hide glue is only that made from skin). Today it's still widely used by woodworkers, especially those engaged in making and repairing stringed instruments.
Animal glue is also used as a paint sizing, the substance in which the pigments are dissolved and by which they adhere to the canvas. Plains Indians used a thin solution of glue for painting buckskins. It's supposed to soak partly into the hide, remaining semi-flexible - the rough, "open" finish on brain-tan probably helps with the absorption. Since the most common leathers of the ancient Mediterranean were similar to brain-tan, this sounds like a plausible solution for us.
Standard "hot" hide glue must be held at around 140 degrees Fahrenheit while working: colder and it will gel, much hotter and the collagen will begin to break down, weakening it. However, hide glue can be kept liquid at room temperature by the addition of an anti-gelling agent, commonly salt or urea. While I can't prove that it was used historically, urea was always readily at hand in the form of urine. That may sound disgusting, but when you think about some of the things people had to do to make leather, adding pee to glue suddenly doesn't sound that farfetched. Thankfully, we don't have to trouble ourselves with that, because premixed liquid hide glue is already available at some hardware stores.
While liquid hide glue has a lesser reputation than hot hide glue due to the urea weakening its bonding power, and unused portions will break down over time, Stephen Shepherd of Full Chisel has argued that fresh liquid hide glue is still one of the stronger glues available. In any case I'm not sure whether the strength of the glue is as critical in painting as it would be in woodworking.
There is one other consideration: While Greece is pretty dry in the summer, most of our stuff would have been exposed to rain sooner or later in ancient times. Hide glue isn't waterproof by itself, but can be made highly water-resistant by the addition of a small amount of alum. Again I have no reason to think this was done, but alum was used as a mordant and leather tannage, so it was at least available. The containers and brushes used with glue that has alum added, must be washed thoroughly before the paint dries or it will be difficult or impossible to wash out afterward.
Materials and methods
Liquid hide glue
Water for diluting glue
Alum (aluminum sulfate)
Earth pigment
Suede leather scraps
Alum is recommended in amounts of 1-2 percent. Too much can cause the glue to gel prematurely. Assuming it has a similar weight to salt, for one ounce of glue (before dilution), I estimate one twentieth of a teaspoon would be the correct amount, but since it's so hard to measure in such quantities, I'll try it by eye - slightly less than half of an eighth of a teaspoon ought to be close.
In order to mix the alum thoroughly into the glue, it should probably be dissolved in the water first. An exact ratio of water to glue is not given in the Crazy Crow instructional, so I'll begin with a 1:2 ratio which hopefully won't make it too dilute to begin with. Let's start with a tablespoon of glue, a teaspoon and a half of water, and half of a half of an eighth of a teaspoon of alum.
The bottle on the left is a modern acrylic leather paint I have on hand, which I'll be comparing to the hide paint to see whether it's acceptable as a more convenient substitute.
Questions
Does hide paint remain flexible enough when dry for use on soft leather goods (gorytoi, bags, clothing)?
Does waterproofing with alum affect the paint's flexibility?
Does acrylic leather paint provide a similar appearance and degree of flexibility and water-resistance to alum-treated and alum-free hide paints when used on the same leather?
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