Casing

Greetings! Today I shall deliver an excessively long lecture on casing, aka, getting leather properly wet in order to carve it, tool it, and mold it. (You will be astounded how many words I have to say on the subject of “get it wet.”) Casing is not the most glamorous part of leatherworking, but it is an important one – properly cased leather will give you better results on your finished product, and also make the process easier and more fun. Working with good, properly-cased leather is a genuine joy – working with cheap or badly-cased leather is an exercise in frustration.

I haven’t really found anywhere else that puts all this information in one place. Other people have talked extensively about tooling, because that’s the fun part, but I’ve never seen a comprehensive guide on casing. When newbies get on leatherworking forums, etc, and ask for advice on casing, the old-timers tend to say things like “You’ll learn to tell when it’s properly cased” or “You’ll get a feel for it” – which is true, but not all that helpful when you’re first starting out.

So, what kind of projects do you need to case your leather for? In short, anything that involves molding, rounding, or shaping, anything that has that nice three-dimensional curve to it…

…Or tooling, which is when you put a design in leather by carving and stamping it:

…Or both. Most of the projects I do involve both – I tool the design onto the surface and then shape them into something wearable.

Note: casing is for VEGETABLE-TANNED LEATHER ONLY.

Chrome-tanned, aka garment leather, the soft and colorful stuff that’s used for leather jackets, pants, upholstery, etc, doesn’t have any of the same properties as veg-tan. It’s usually got a glossy, textured surface on one side and suede on the other. (Or suede on both sides.) You can’t mold it, you can’t tool it, and if you get it wet you’ll only ruin it. This is chrome-tan:

Meanwhile, veg-tan is this stuff:

Veg-tan comes in one color, that distinctive pinkish-tan, and it’s much stiffer than chrome-tan. You will not be sewing any clothes out of veg-tan, it’s for belts, shoes, hard-sided bags, and armor. This is your tooling leather. It should be smooth, not textured, with a matte surface. Don’t worry about the color, veg-tan is very good at taking dye, which chrome-tan is not.

(For a longer discussion of chrome-tan vs veg-tan, see the post I dedicated to the subject.)

Honestly, I think it’s incredibly confusing for beginners that both of them get referred to as just “leather” without any qualifiers, since their properties are as different as worbla from denim. So if you’ve accidentally bought chrome-tan, put it away, save it for another project, go get some veg-tan, and come back.

Okay? Okay.

Veg-tan leather is a lot like a sponge – it’s a bunch of interconnected fibers that soak up water extremely well, and when it’s wet it becomes quite malleable. I like to call it the medieval version of plastic, because of how incredibly versatile it is.

The key to casing is to make sure that your leather is wet all the way through, right to the core, because you’re not going to get the right results if the core of the leather is still dry – it’s not going to stretch (for molding) or cut deeply (for carving) or compress (for tooling). You need to let the water penetrate all the way through – and then you need to let some of it evaporate off again.

This is the essence of proper casing: that the core of the leather is damp, but the surface is relatively dry. It allows the leather to hold a new shape when you stretch it, but also allows your stamping to be crisp instead of squishy.

You soak the leather with more water than it needs and then let it start to dry out  again. “Properly” casing the leather just means being able to identify when it’s at the sweet spot between too wet and too dry. The old-timers are right when they say you’ll learn that from experience, but seriously, it’s not voodoo and it’s not rocket science – they just know what to look for, and after you read my cheat sheet, you will know what to look for too.

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So, rookie mistake number one: just getting the surface wet. Spritzing it with a spray bottle, running it briefly under the tap, etc, isn’t going to do the trick. That gets the surface of the leather wet, but it’s going to evaporate long before it gets to the core, which is the part that actually needs to be wet.

Fill up a bowl with water (or a sink, depending on the size of your project), and then submerge the entire piece in the water face-down. It will start wicking up water immediately and you’ll be able to see it bubbling and fizzing as the air inside gets squeezed out and replaced with water. No need to fold or bend it, just put it underwater and hold it there.

Or if you’re doing in bulk:

You don’t have to hold it under until it stops bubbling altogether, because you don’t need the piece to be completely waterlogged – recall that the goal here is to get it wet enough that the water can work its way to the core. But when you’re just starting out, before you have a good feel for what the right amount of saturation is, you can err on the side of caution by holding it under until the fizzing stops or until it slows ways down. Being over-saturated doesn’t do it any harm – it isn’t going to hurt the leather or damage your project, it’ll just take longer to dry out before it’s usable.

When you pull the leather out, you’ll see the water on the surface disappearing as it’s absorbed into the leather. The leather also becomes much more flexible as the water penetrates – flexibility and speed of absorption are your main indicators of how saturated the leather is.

Hard to show in a freeze-frame, but that water is actively disappearing into the leather. Ten seconds later it was gone altogether.

If the leather is still very stiff, you should probably give it some more time underwater. (On the other hand, if it’s gotten all soggy and floppy, you’re done.) Or if you take it out and the water on the surface is immediately sucked into the leather, it probably needs more time. (Conversely: if the water on the surface is just sitting there, ie, the leather is no longer absorbing water, it’s done.)

A good level of wet: leather that is still absorbing water, but rate of absorption has slowed.

So how long do you hold it underwater to reach that “good level of wet”? That’ll depend on the thickness and the density of the leather.

For thin leather (up to 5 oz, re: ~1.5 mm), a couple of very quick dunks is usually all you need, we’re talking just a few seconds at a time, adjusting your grip on it so that your fingertips don’t leave dry spots. Thin leather reaches saturation very quickly – but it also dries out again very quickly, so it’s not a big deal if you overshoot.

For thicker leather, it will vary greatly depending on density. For leather in the 8-10 oz range (about 4 mm), some of it will be completely soaked through in under fifteen seconds, some of it will still be fizzing even after several minutes underwater.

Leather that’s very spongy and porous will soak up water MUCH faster than dense leather, and then it’ll take commensurately longer to dry, because it’s carrying more water to get rid of. You can identify spongy leather because (1) it has a looser grain on the underside, one that likes to tear away from the rest of the hide if you pull on it and (2) it’s relatively flexible, even when it’s dry.

Whenever possible, you want to get leather that looks like the stuff on the left, and avoid the stuff on the right.

Leather that’s exceptionally dense will take a very long time to absorb enough water, since the water has a hard time working its way in. You can recognize super-dense leather because it is VERY tough and difficult to bend, and after you put it underwater there’s a noticeable delay before it starts bubbling.

When the leather starts absorbing water, it immediately becomes much darker (though don’t worry, it will return 100% to its original color once it’s dried).

Be careful not to get spatters of water droplets on dry leather, unless it’s going underwater almost immediately afterward, because it will leave circles on the leather where it swells and then shrinks back down.

So, looking at some pictures:

Judging by the flexibility, this is where I would stop. It’s not completely sodden and dripping, but it has enough water to migrate to the core.

Soaked. If the water is pooling on the surface and NOT being absorbed, it’s more than saturated. If the water is still being sucked into the leather very quickly, give it another couple few-second dunks.

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That’s the protocol if you’re preparing leather for tooling or doing some moderate shaping to it. If you’re going to be subjecting the leather to very dramatic stretching and shaping (such as using a mold), I’ve heard people recommend leaving it underwater for as long as 5-10 minutes. This will ensure that every last bit of air has been replaced with water, and the leather is as malleable as it’s ever going to get.

The next step is to put the leather in an airtight (or airtight-ish) container and let it sit for many hours, so that the water it has absorbed can disperse evenly through the fibers. I usually put it in a plastic bag (gallon ziplock bags if it’ll fit, plastic grocery bags if it’s too big for that), and let it sit at least overnight.

The key is uniformity: you want to get water dispersed evenly through the leather, not drying out in some patches while staying soggy in others. It’s still not an exact science, because the density of the leather affects the speed of absorption/evaporation, and the density of the leather can vary even across the same piece, but you do the best you can.

That light blotch is a patch where the leather is denser and therefore not absorbing water as quickly as the surrounding area. All you can do is keep applying water to that one patch specifically and try to make it even out.

There is no such thing as over-casing, so it can sit in that plastic bag indefinitely. The most beautifully-cased pieces I’ve ever worked with tend to be ones that have sat in the bag for a couple days, or even a week or more – but if it’s going to be more than a few days before you get the chance to work with it, I strongly recommend putting it in the fridge so it doesn’t start to grow mold. Chilling doesn’t do your piece any harm, but mold definitely will. 

(Freezing, mind you, WILL ruin the piece, so be careful if you’ve got a fridge that likes to freeze things.)

I tend to let it sit in an airtight environment (ie, the ziplock bag) for the hours that it’s soaking, so that it doesn’t risk drying out while the water is working its way to the core of the leather; then a little while before go-time, I take it out of the bag and let it sit exposed to air to get the surface of the leather to the right level of dry.

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So I said that “properly cased” is the sweet spot between too wet and too dry. If rookie mistake #1 is trying to work with it when it’s too dry (aka, just dampened on the top surface), then rookie mistake #2 is trying to work with it when it’s too wet.

It is too wet for tooling if:

– The color is still as dark as when you first pulled it out of the water

– It’s still sodden and floppy (won’t hold a curve, just falls over)

– When you press on the surface of the leather, with a tool or even with just your finger, you can see water rising in the indentation:

– The leather doesn’t change color where you indent it (it all just stays the same level of dark) 

– The surface has noticeable friction – it “drags” on your stamps and your swivel knife, tugging the leather in the direction your tools are moving. You find your tools catching on it and making a lot of mini-jumps instead of gliding smoothly along the surface.

– The leather is too squishy to hold a shape. When you hit it with a stamp, it makes an indentation, but then when you make an adjacent stamp, the previous section squishes right back up instead of staying down. Makes for very lumpy tooling. Also if the grooves you’ve cut with your swivel knife are too soft, and your stamps are trying to walk over the line instead of being guided by it.

If it looks gross when you tool it, it will not get any prettier when it dries:

(So that tooling is awful, the way you can see the individual lumps from every stamp strike, but in my defense I was working under seriously sub-optimal conditions: the piece had already been dyed, sealed, and shaped before I decided to take it apart again and add more bling. It was a nightmare to work with, and the results are not nearly as good as if I’d done it correctly from the start.)

If you’re putting a dramatic curve in the leather, like the kind of rounded pauldrons where you’re practically wrapping it around a bowling ball, you can do a lot of your preliminary stretching while it’s soaking wet, but you can’t make your final shape – unless you’re letting it dry over a mold, it’s too floppy and won’t stay in the shape you put it.

This is also a good time to point out that leather is not a particularly forgiving medium – once you put an indentation in it, there is no way to get it out. If you scratch it with a fingernail, miss the stamp and hit the leather with your hammer, or space out and stamp in the wrong place, that mark is there to stay.

(For this reason, I recommend against wearing bracelets, a watch, or cuffs with buttons on your non-dominant hand when you’re tooling – you’re likely to roll your hand wrong and leave unwanted dents in your project. And if you’re bored, cold, and/or tired when you’re tooling, you’re likely to miss the stamp and hit the leather with your hammer, just sayin’ is all, not that I’ve ever done that. >_>) You can smooth out very shallow dents/scratches with the back of a spoon, but really, it’s better to just be careful.

If you’re hitting any of the points on the “too wet” list, there’s an easy solution: let it dry. Leave it out on the shelf and go do something else. Depending on temperature/humidity/etc and depending on how saturated you got your leather, this can sometimes take many hours. Check back on it periodically to see whether it’s ready.

You know your leather is at the sweet spot when:

– The color is starting to look dry again

– The surface of the leather feels dry, but is still slightly cold to the touch. (You can gauge this better by pressing it to your cheek than trying to feel it with your fingertips.)

– It has regained some of its stiffness, and will hold a curve if you bend it

– Swivel knives and stamps should be able to glide across the surface without sticking or catching.

– It takes stamps beautifully and gets that lovely dark burnishing where you hit it.  Properly cased leather will actually change color when you indent it, either with a stylus or with a stamp. The effect is called burnishing, and it’s vital if you’re going to be keeping the leather its natural color, otherwise your design won’t show up very well.

When it’s at the right level of casing, you can put it back in the bag until you’re ready to work with it, and also between steps. This will halt the drying, and keep it at the perfect state until you have time to do the next step. Trace the lineart – back in the bag – carve your cutlines – back in the bag – do your stamping – back in the bag – shape it – now you can let it dry. 

You’re probably not going to accidentally let the leather dry too much before you start working with it (because we’re all eager to get on with our exciting projects, yes?), but if it’s a large piece and you’re working in a warm, dry location, it’s not unusual for the piece to get too dry before you can finish it.

Amount of saturation, plus air temperature, ventilation, and humidity will affect how quickly it dries – leather will dry slower indoors than out, and slower in the shade than in the sun. I STRONGLY recommend against carving and tooling in direct sunlight – it gives you precious little time to do your thing before it’s too dry to work with.

My advice is work quickly, work in the shade, work from the outside in (because edges will dry out faster than the center), and when you’re not actively working on your piece, put it back in the bag to keep it cased until you come back to it. Other people have recommended covering parts of your project to keep them cased until you’re ready to work with them.

Once you’ve started carving/stamping, you can’t soak the leather again without fucking up the work you’ve already done. You can buy yourself more time by carefully administering more water with a damp washcloth/sponge to the underside of the leather, but avoid applying water to the surface that you’ve carved or stamped – you don’t want water in your cutlines or they will become swollen and less sharp, and you’ll lose a lot of your fine textures.  

The leather is too dry if:

– The color has entirely returned to its original state

– The temperature of the leather is as warm as the surrounding air

– It gets harder to stamp – you find yourself having to whack the stamps harder in order to get the same depth

– Your swivel knife won’t cut very deep into the leather

– If you bend the leather, it springs back to its previous form, you can’t give it a new shape.

– The color doesn’t change where you indent it (stays light)

Too dry is a better mistake than too wet, in my opinion, but it does put the time crunch on.

**

So what do you do with it, now that it’s properly cased?

Now you get to tool it, which is usually the step that tutorials on leatherworking skip directly to. You can google it – “leather tooling/carving tutorials” – and someday I’ll probably make one myself.

If you’re going to do both tooling and shaping on your project (such as decorated armor) your order of operations is crucial: you HAVE to tool it before you shape it, because you can only tool leather when it’s flat against your work surface – once you’ve put a curve in it, it’s going to be difficult-nigh-impossible to stamp.

Moreover, you can’t let it dry out between tooling and shaping, because you can’t re-case it after tooling – it’ll kill the details in your design. If there’s going to be a delay between finishing your tooling and working it into the final shape, put it back in the plastic bag and seal it up again. Putting it in the bag again halts the drying process, and it will remain at the same level of cased almost indefinitely.

Other things to do while your leather is flat, before you shape it:

– Round off your edges – with an edge beveler if you’ve got one or with an exacto knife + sandpaper if you don’t. Not only is this more easily done when the leather is still flat, before you stretch it into a three-dimensional shape, but damp leather is also kinder to blades than dry leather. (Like how your stylist gets your hair wet before cutting it.)

– Punch any holes you need. Seriously, hole punching can be a pain the ass when your piece isn’t flat.

And now, once you’ve done everything else you can conceivably think of to your project, stretch it into the shape you want, and prop it up to let it dry.

How long it takes to fully dry will depend on a lot of factors – temperature, humidity, the thickness of the leather – but in general it takes armor-weight leather about 8 hours to mostly dry, and by the 24-hour mark it will be totally dry. (This is why tooled projects take at least a couple days, even if I were to be working on nothing else – the hours needed to case, the hours needed to dry.)

Now you can apply your finishes, edge coats, waxes, etc, and assemble your final project.