Blackening revisited

[ToddM]

Greg, when you say 1:7 ration is this hot water to Jax or vice versa?

 

Thanks for this tutorial. I was having difficulty getting results. I will try this method.

 

Todd

 

 

[Justin P.]

Can someone please comment on how you typically dispose of the blackening solution and the spares once your done?   Ive used it (Jax specifically) several times and have been reluctant to send it down the drain.   Ive mostly just used it sparingly and then soaked it up into used shop towels and then hang outside to evaporate.    How is the Sparex disposed of?   How are you cleaning the crock pot for storage?   

[BANYAN]

Hi Justin,  I also had concerns.  I only make up small batches at a time in a small glass jar and reuse it as much as possible.  If stored in a darkened area (no direct exposure to sunlight), or in a dark glass jar (I prefer clear as you can monitor the chemical process when using it), you can store and reuse it for up to a year or so at a time depending on how much you use it.  If the solution starts covering/blackening erratically, or takes much longer to be effective, it is time for change.  One sign I look for is that the solution does not return to a relative clear state  some time after use, then it is time to start looking at a new batch.  The bluer it stays, the less effective I find it works (after use and letting it sit for a while).

 

To dispose of it, I find an area in my garden where it will have minimal contact with tree/plant roots etc, pour the solution onto a thick bunched up wad of paper towels and then let the paper dry.  The paper tends to filter the solution  (not completely); once dry I throw the paper into the waste (general waste not recyclable).  Still not completely removing the chemical residue from waste but better than pouring down the grey water drain?

 

cheers

 

Pat

[dvm27]

On 3/7/2020 at 1:53 PM, ToddM said:

Greg, when you say 1:7 ration is this hot water to Jax or vice versa?

 

Thanks for this tutorial. I was having difficulty getting results. I will try this method.

 

Todd

 

 

The ratio is one part blackening solution to five to seven parts water (precision not required here).

 

On 3/8/2020 at 2:45 PM, Justin P. said:

How is the Sparex disposed of?   How are you cleaning the crock pot for storage?

I keep my Sparex in the crock pot, covered, for months on end and reuse as needed. When finished it can be neutralized with baking soda and flushed. Then just rinse out the crock pot. Never leave your crock pot unattended for a day or so or you will be purchasing a new one!

[bartley]

I actually posted this elsewhere but it is probably more appropriate here.

 

This is an example of a blackening problem which others may have experienced without knowing the reason.

 

These belaying pins were sold as being brass so on the right I used my usual technique of treating for 5 min with sodium hydrogen sulfate then blackening.  Even after about 1 min the result was poor.

On reflection they were very shiny so were probably lacquered. So on the left the treatment was: - rub with steel wool, soak in acetone for about 1 min, 5 min in sodium hydrogen sulfate then blackening. After only for 10 sec the result was excellent.

 

 

Incidentally, Sparex is just a very expensive packet of sodium hydrogen sulfate. So if you have access to the chemical itself it is much cheaper

 

John

 

[bartley]

On 3/9/2020 at 4:45 AM, Justin P. said:

Can someone please comment on how you typically dispose of the blackening solution and the spares once your done?   Ive used it (Jax specifically) several times and have been reluctant to send it down the drain.   Ive mostly just used it sparingly and then soaked it up into used shop towels and then hang outside to evaporate.    How is the Sparex disposed of?   How are you cleaning the crock pot for storage?   

Justin,

 

Yes, disposal is always an issue.  I am a professional chemist and so disposal is part of our trade.  Sparex once dissolved is essentially sulfuric acid. So to dispose of it you should pour it slowly into bicarbonate.  It will fizz so do it slowly.  Once the fizzing stops the Sparex is neutralized and you can dispose of it down the sink,  The blackening solution is another matter.  This, when fresh, is selenious acid.  When you use it it is converted to black selenium metal  and copper sulfate That's the blue colour.  But you cant neutralise or destroy the selenium. or copper.  So a spent solution contains selenium in one form or another and copper sulfate.  Neither of these is too good for the environment but you only have small quantities.  You shouldn't dispose of it down the sink so absorbing onto paper and burying it is probably OK.  Over here we can take such things to a toxic chemicals disposal site.

 

John

[bartley]

On 9/1/2019 at 1:56 AM, kurtvd19 said:

It is important that the Sparex doesn't boil (can't remember the exact hazard that results) but the crock pot can't get hot enough to boil the liquid.  So any heat source that doesn't boil it is OK.  The crock pot is perfect because it's got no metal - remember Greg's warning about using copper tongs - Sparex can't be stored or used in a metal container.

Kurt

Yes indeed Kurt, boiling Sparex (which is incidentally an expensive packet of sodium hydrogen sulfate) could be dangerous because once dissolved it is sulfuric acid.  It is quite dilute initially but if it becomes concentrated by boiling it will produce oxides of sulfur (chemically SO2 and SO3). These are dangerous gases and if inhaled could cause permanent respiratory damage.

 

John

[bartley]

On 8/31/2019 at 9:20 AM, dvm27 said:

or those of you who have had hit or miss success with blackening I have found the following techniques to work consistently and create a durable finish that won't rub or flake off. Most of the products are available from Beaducation, a jewelry supply store that also has great learning videos https://www.beaducation.com/pc/393-jewelry-making-tools-soldering-fusing-tools. Check it out.

 

 

 

See also my post here on the chemistry of this process and its consequences on the practice of blackening 

 

John