Disposing of Old Ferric Chloride Etching Solution
This article will cover the safe disposal and replacement of old ferric chloride etching solution.
The etching tank that is usually kept under the sink in the main workshop contains a solution of ferric chloride that is used to remove unwanted copper during the etching process. This solution will become weak with prolonged use and will eventually need to be replaced, however due to the nature of the chemicals involved and the fact that it will contain copper, a heavy metal that is bad for the environment we cannot simply dispose of it down the sink and into the water system. This along with a few other safety reasons requires us to dispose of the old solution safely.
=
Equipment Required: ===
- Safety goggles,
- Fask mask (optional, protects against splashes)
- Gloves,
- Apron or old clothes you don't mind getting stained. Long sleeves would be a good idea.
- Bucket
- Funnel
- Large plastic or glass bottles - 3-5L total capacity
- Sink
=
Disposing of Old Solution: ===
- Place the bucket in the sink,
- Remove basket/lid from the etch tank,
- Pour out the old solution from the BACK of the unit, not the front or sides.
- Rinse the inside of the etch tank and pour into the bucket,
- Place empty bottle in the sink and place funnel in the bottle neck,
- Pour the solution from bucket to bottle, repeating until bucket is empty.
- Put the lid(s) on the bottle(s) and label with sticky label and marker pen "OLD FERRIC CHLORIDE ETCHING SOLUTION - DISPOSE SAFELY"
- Store labelled bottles under the sink in the main workshop.
- Notify the trustees that the solution needs to be disposed of. They will arrange for it to be taken to a suitable disposal site.
Creating new solution
- Take 2-3 packs of ferric chloride crystals for etching, available from various suppliers, check online.
- Dissolve each pack in 1-1.5L of water and pour into the freshly cleaned etch tank.
It may be worth running the the bubbler and heater for a few minutes just to help the solution mix up nicely, especially on a cold day. You want to make sure that the solution fills enough of the tank to completely submerge the board you are etching. Add more water to the solution if needed. Be aware you may need increase your etch time or add more ferric chloride crystals to account for the dilution caused by adding more water. Once this is done, you're ready to start etching again.