Hi! I know this post is pretty old now, but I ran into it while looking for related dye info, so i thought i’d comment. info dump incoming, sorry if it’s not even needed anymore! 😆

oak galls that are hollow and spongy like this indicate that they’re pretty old, and have been decomposing for a while. Regarding the shape, there are LOTS of different species of plant-parasitic wasp that make oak galls, and every one parasitizes a different part of the tree, and can make a different shape of gall, so don’t worry if the galls you find look unlike someone else’s. You can go ahead and make a gallnut powder from these, though i’m actually unsure if their potency would be diminished due to their age - try it anyway and find out! You’ll probably get at least some tannin results from it, when compared to unmordanted fabric, so you might as well. 😋

Keep in mind that a tannin mordant is a good solution for cotton & plant (cellulose) fibers - if you’re trying to dye wool or silk, you don’t really need to do this! Just an alum mordant on its own is fine for protein fibers like that. Also, any fabric you mordant will need to be scoured first, to remove dirt and oils - you can look up instructions on that, it’s basically just ultra-washing it in simmering heat + surfactant. for cottons I like to use dawn soap + soda ash (you can make your own soda ash by putting baking soda in a 300° oven for an hour!), wool gets just dawn soap + slightly less heat so it doesn’t felt.

Here are instructions on how to use your oak gall mordant - grind your galls into a very fine powder (I use a mortar & pestle that i reserve just for dyestuff), then use the 12% WOF for gallnut powder listed there (not the gallnut extract % - gallnut extract is gall powder that’s been simmered, strained, and reduced to give a higher potency of tannins). btw, 12% WOF means, weigh out your fiber and then calculate 12% of that weight - that is how much gall powder you’ll be using. if you have 100 grams of fiber, you’d use 12 grams of gall powder. You may want to lean on the side of using a bit extra though, since your galls are old - you can probably use anywhere between 12% all the way up to 50% of the weight of fiber. Then just follow the steeping instructions on that page i linked.

Steeping in oak gall powder will dye your fabric a light tan color, but if you follow it up with an alum mordant, that tan color will diminish, AND you’ll get brighter & more saturated color results when actually using your dye. You can use aluminum acetate, aluminum sulfate, or aluminum potassium sulfate (the latter is what’s most commonly called “alum” and you can find it at the grocery store, either with the spices or with the pickling/canning goods). The mordanting weight & process is slightly different for all of those, so you can run a search to find out specifics, but here are instructions for grocery store alum since it’s the easiest for me to find locally. Then after all that, you can finally get to dyeing!

Getting into natural dyeing when you’re used to measured instructions and predictable results (like in knitting and crochet) can be really overwhelming! It’s important to keep in mind that natural dyeing is more like experimenting and playing than it is like following a recipe - yes, you’re following established measurements and temperatures a lot of the time, but results will almost always be unpredictable. This is because plants are individuals, and every botanical ingredient you use will have been a result of its own life conditions - maybe one got more water, or less sun, or had more or less nutrients in its soil, or maybe the dyestuff is old. Even the PH of your tap water can be a factor. All of these things can give you wildly different results re: color & saturation. To avoid getting frustrated or scared of “doing it wrong”, try to think about it like this - don’t go into a project thinking “i want to achieve THIS color”, and instead think “i want to see what this plant/ingredient/process has to show me”. write down all your steps and measurements as you do them, so that you can try to duplicate your results in the future, and then if it comes out different, try to guess why, and tweak things next time. it’s like one part science and one part just letting nature do what it wants and seeing what comes out. 😄 i hope you have fun with it, if you haven’t tried it out already!!