Hi MM , best keep your money in your pocket until you have the info you need ! It is very hard to track down as it is either hidden in obscure corners of the internet or dispersed widely in fragments here & there , if it is even there at all ! Talking to a pigment "sales person" might well end up with them selling you some pigments without any specialist knowledge of using the pigments specifically for ink making - that's very rare for good reason.
Here's a run down though some of the hurdles in this ink making challenge - you may choose not even to take the challenge on ,OR approach the task in a different manner
1.Yes shellac is dissolved in ethyl alcohol ,that is freely available on Amazon or ebay etc. Don't worry your work with this ink will still be 100% fully archival as long as your pigments are of course.
2.After you have dissolved the shellac into the ethyl alcohol you will want to add water to it & get it to the correct viscosity, THIS MUST BE DISTILLED WATER otherwise the chemicals that municipal authorities add to clean it OR just the air pollution in it will separate the pigment from the shellac making a useless gunge ! If you live a bit out of town & traffic you can capture rain water ,put it though a coffee filter & use that ,but hell the distilled is widely available & cheap anyway. This distilled water rule applies to any & all shellac based inks commercial or home made.
3. Now the hard part Pigments used in ink & paint are from exactly the same basic source BUT
the pigment in any ink has to be ground up VERY much more finely so that it can hold it's suspension in the aqueous mix. You can very
occasionally find an extremely
specialist supplier BUT
even if you find such a supplier the pigments ground at this very small size in their dry powdered form can be very hazardous to your heath , both the risk of inhaling them & the toxicity plus the the fire risk should they become air born, certainly a professional vented closed cabinet is essential
So as you can see this is not really a viable option even for keen experimental artists like us !
Much better is to buy a ready made pack of coloured commercial shellac inks.Search "coloured shellac ink" or blue ... or yellow... & definitely "coloured India ink" & "coloured encre du chine" I know A few english suppliers but that might be expensive. Another problem is that many of these use a modern permanent dye to colour their inks, whilst they may be extremely vibrant they might not suit you,obviously you can mix inks from the same manufacturer in an attempt to get your perfect colour & maybe ?(it just depends) from different manufacturers.Difficult anyway though because there aren't that many colours available in any commercial range.
Ah ! you like Rembrandt (me too!) & his inks, I have studied him & his materials extensively. .Well he certainly didn't use any shellac in his ink !
For years & years it was supposed that he used "Bistre" pigment (Burned beech nut soot") , still I read that all over the net but when the museum in Amsterdam used the non destructive but totally conclusive spectrometer analysis hundreds of years of a "best guess/assumption" by non artist academics was turned on it's head !
He in fact used Iron gall ink, a gall is a growth formed on an oak tree which is made in response to an attack by a certain wasp. (You can buy these !)
Add some rusty nails to vinegar & let them soak some time then add your galls & let it soak for a while longer. There you go ! you have the ink of the early christian church ,though Michelangelo , Leonardo,Raphael etc. Hold on a minute ! lots of them used black ink I here you say.
Well yes, Iron gall ink is often a very dark brown but it depends on the proportions of the ingredients in the mix as to the final colour. PLUS the drawings we are looking at today have had centuries of oxidization , however the mixes were all individually made & many of Rembrandts fellow artists of the same time used the same type of ink & it is still very dark brown. He chose to do it that way !
You can still buy made up iron gall ink but it will be very dark brown/black.Funny thing is it is very acidic & not so called archival ,despite the evidence !