BPO: Dark Backgrounds

תיאור השירות

Tannins & Ferrous Sulfate In this module we will first recoup the previous knowledge learned. We have seen that a ferrous sulfate mordant reacts strongly to the tannins in leaves, creating a dark print. ​We have also see that a tannin bath with an iron dip (post mordant with ferrous sulfate), results in a dark fabric. This was the p[roper way to make dark greys and blacks up until the 19th century, when after 1830 synthetic dyes, derived from coal tar, started to take over. ​We will now use this principle to create a dark background Pro Tip: When you use extracts of tannins (or natural dyes) there is no need to rinse the fabric (we prefer to keep all the dye materials 'in'. When you are using powdered materials (like pomegranate rind) you must rinse the fabric well, to remove all little bits and pieces or they will show up in your final results. Alternatively you can choose to put the dye material in a very fine mesh like an old pantyhose. However: I have found this does not always work as well as simply rinsing the fabric. How much tannin to use for your blankets? For extracts: You will make a rather concentrated solution, do not use a ton of water for this. For extracts as a rule of thumb we use around 20-30% tannin extract (quebracho, Cutch, acacia) but keep in mind: suppliers have varying stock and not all extracts are alike. If you see it is super dark: use less, if you see the results are rather light to your liking: use more. This is exactly why we make test strips. For powdered tannins: check if it says on the website how much the tannin % is. Example: my oak gall powder is 70% Tannin content. 25% of oak gall powder is enough for a blanket. Sumac powder is much less, so I would increase WOF to 40%. Also keep in mind that powders need to be rinsed off so you may want to keep the blankets longer in solution, and/or use a mesh bag (like an old pantyhose) to keep the powder in check. Exercise no 1 . Take a 20 cm strip of ferrous sulfate mordanted fabric (the fabric you have mordanted in the mordants module). Wet out if needed, squeeze very well. .​Take 20 cm of your blanket material that you have given an acacia tannin bath. No need to rinse, this is extract, just squeeze all the excess water out. .If you are using a powdered material for some reason you will have to rinse prior to using. . Start making your 'sandwich' by starting with a barrier, then smoothen your ferrous sulfate target fabric, lay ONE type of tannin rich leaves