Sure you can use Sodium persulfate in those etchtanks, it's great.
I on the other hand have never tried Ferric in one of those. So that works too?
Back when I was reading the instructions, they were saying "do not use Ferric in
this tank", but hey, if it works anything's game ;D
I started with the little one too, then got the big one, and then did something I should
have done right from the start: I built one.
The big ones you can buy (I had the ISGRAV2) are clear acrylic which begins to break
after about a year or two, and if you look at it what you get is a mediocre pump, a
thing to put a balcony flower pot in (it really is) and some plastic with a heater and
an aerator you'll replace anyway.
So what I did next was to go to my local glass dude who cuts windows and stuff
and had him cut some 5mm glass to my measurements according to the one I had.
Only, I made it bigger, because if you wanna fill an entire 19", it's juuuust not quite
big enough, which is a bummer.
So you get 3 panes of glass 50cmx35cm, and then 1 pane like 51x15cm and 2 panes
35x15cm, respectively. This gives you, for the cost of only one extra glass pane, a
double etchtank that's big enough for everything. You might even go for 40cm
instead of 35 (yes on occasion I wish I had, ask Viitalähde
) Heck, probly costs the same.
For 100€, he made me
two of these monsters, so 2 complete machine bodies à 2 tanks.
Then you go out and get silicone (really good aquarium silicone, not the cheapo stuff)
and you silicone it all together. You can use stacks of coins to keep the distance between
the 3 big glass panes and the work surface.
You can make the tanks about 3-4cm thick each, might wanna check how big they
have to get so you can comfortably fit those Sander wood blocks in. At 30cm liquid
depth, each cm cuvette thickness will be 1.5 Liters of acid (one Fanta bottle, haha).
So now you're at 112€ approx. for 2x the capacity, way bigger and lasts forever,
plus you have two entire machines so that's 4x the capacity (haw).
Of course you can build 4 tanks into one machine if you feel funny that way.
Then you get 2x heating stick but not "Réglage de la température de 20 à 32 °C."
You want 48°C, haha.
So you get this here:
http://www.conrad.de/ce/de/product/530425/HEIZUNG-FUeR-530336-150-W-1185/2512150
Type Speed, distributed by ProMa.
Which is only 150W, but it goes up to 50°C - most of the other ones they sell don't
because they're for aquariums and you don't want to cook your fish by accident
So now you can get two of them for the double tank, then get yourself the right
pumps, and wood aerators, and silicone hoses and all, you're also up to about 250 €
but yours is waaaaaaay cooler and lasts for ever.
Then all you need is a thermometer, and you're ready to go.