making up etching solution

[Simon]

So I have my nice 2L bubble etch tank and have aquired the 1Kg of ferric chloride crystals to put in it. The instructions say to mix it up at 35C with 1/2 the total water and then top up. the solution is to be used at 45C, why the 10C difference ?

I was just going to put about half the water in the tank and heat it up to 45C with the provided heater slowly pour the pellets in and let the air bubbles and natural convection of the heater do the mixing although I'm sure I have a stick or something to do a little mixing

[ElektroQuark]

No problem doing it at 45ºC. The suggested temperature is a minimum so the dissolving time is minimized.

[Simon]

oh right

[ElektroQuark]

On the other hand, it is not necessary to heat the solution, but at normal temperatures the etching is very slow.

The FeCl3 is very aggressive with the metal surfaces and it will also stain everything it touches. Be aware.

[Simon]

yea, I'm moving from a 1L cereal box to a proper 2L tank

[mikeselectricstuff]

Mixing isn't at all critical, but is quicker when warm. Keep adding the granules til no more will dissolvbe. DO NOT add water to a clump of dry granules as it can be somewhat exothermic. You definitely want it warm when etching as it goes lots quicker - about 40-50 deg C is a good compromise between speed and fumes.
Solution should be 'clear' brown - if your solution ends up cloudy light brown/yellow, add a pinch of salt. 

[Simon]

Well it is sitting there simmering away, worked a treat, just added the crystals one bag (250g) at a time to half the water heaters up and the bubbles make quick work of aiding their dissolving, then topped the level up. The only hiccup was that the heater would not go far enough into the half tankful of liquid to cover the min level mark so used a smaller heater to get the initial solution up to temp

[Psi]

Just a heads-up, ferric chloride will ruin clothes if you get it on them.  It will either eat away at the fabric or remove the dye depending on the type of fabric and what other chemicals its been treated with.

[Simon]

yea, i always use old cloths when etching, one of the pluses of getting the proper tank is that I will be less prone to having mess caused by the fact that the cereal tub was a bit small and not having a bubble system or board clips/hook I was holding the board with a gloved hand and rocking it in the solution to help remove the copper, now I can just dangle it and observe