A question for the chemists out there-re: Pickle-It

[wldlzrd1]

Hi,

ok, i have posted about this topic a few times in the past, and am hoping someone with chemistry knowledge might be able to solve a mystery

why is it, when using Pickle-It, the sterling silver metal gets a dull grey stain on the surface? and then darker grey splotches after being submersed in a baking soda/ water neutralizing bath?

here is what i have done so far:

i annealed a sterling silver ingot
i used boric acid/ denatured alcohol as a barrier flux
i quenched in room tempurature water
i cleaned in hot water in a crock pot (set to high)
i rinsed it in tap water
the ingot came out clean

then i put the ingot in Pickle-It in a crock pot (set to low)
after a minute, it turned a uniform dull light grey
Pickle-It was a 1-8 mix ratio with water

then i took the ingot out of the Pickle-It, and put it directly imto a bath of 1 Tablespoon of baking soda and about 3 cups if water
the ingot immediately started to stain a splotchy darker grey

i took a look at the MSDS for it

i noticed under the section “reactivity” it says “yes” to “strong bases- oxidizing agents”

does this have something to do with the reaction i am seeing?

the ingredients listed are:

any thoughts?

i am sooo curious…

julie

[wldlzrd1]

Hi,

ya know…this is making me think of the time i tried “cleaning” my two silver-plated candelabrah, using the foil technique…they turned grey…

i gotta go search for that thread…

julie

[neil_a3]

What possible need is there for iodized table salt?! It wouldn’t surprise me if you weren’t creating silver iodide. Here’s what wikipedia says about silver iodide:

Silver iodide is an inorganic compound with the formula AgI. The compound is a bright yellow solid, but samples almost always contain impurities of metallic silver that give a gray coloration.

See Silver iodide - Wikipedia

Why Zeothix 265? There isn’t much on it, but I found this:

Product Description
Zeothix® 265 effectively absorbs plasticizers and oils to improve flow and to decrease sticking on calendaring rolls.

Why not just use sodium bisulfate or plain citric acid?

Neil A

[Yggdrasil]

@neil_a3

iodized table salt

Iodized Salt do not contain enough Iodine to create a problem. 57g Iodine per 1 000 000g Salt
Anyway one can just use un-iodized salt,
since it is the electrolytic reaction between the Aluminum and Silver that creates the reaction.
The salt makes the water conducting.

[neil_a3]

@Yggdrasil

Anyway one can just use un-iodized salt,

The solution Julie is using is giving her problems and contains ingredients that when left out, as with plain sodium bisulfate or plain citric acid, work just fine. Whichever ingredient is responsible, why use it? There is the acronym KISS which I always say as “Keep It Simple Sam” rather than the usual, and that goes for pickle ingredients.

If I sound a bit abrupt, my apologies. I’m having a lot less fun installing a floating floor than the people who sell this stuff claim. !#%&!

Neil A

[Yggdrasil]

These things are never as easy as they say, but then with a bit of on the hand training it becomes if not easy so at least easier.
When you are finished, it might be easy

[nancylthamilton]

This is from my website: * Sometimes, if I leave silver pieces in my (sodium bisulfate) pickle pot for too long (completely forgotten usually), a silver, matte, gray, “something” coats the silver. It has also happened when I’ve left pieces in the pot for less than an hour and had this happen. I then re-torch and re-pickle (sometimes twice) to remove the gray gunk. I emailed a few businesses (manufacturers) about this, and they replied that they thought the silver was being etched in the pickle and impurities were entering the tiny openings. This is prevalent when pickling items that contain metal clay. Metal clay is more porous than sheet, so given the explanation I was given, that makes sense. Try a different pickle? Change your pickle?

[RickPowell]

I’ve been using the motorcycle battery acid you can buy locally at auto parts store. (sulfuric acid).
It seems kind of weak though so I have to heat it pretty good for it to work it seems to me. I guess it’s watered down quite a bit but makes it safer to handle. I still have a lot of dirty used of it because I need to dispose of it properly.

What’s the best/strongest pickle? The motorcycle battery acid seems pretty weak to me.

[alonzo]

If you like using Sulfuric acid based pickle, go to your local hardware store and buy a bottle of “Liquid Fire” drain cleaner. It’s pretty much full tilt sulfuric acid. Mix 1 part of it to 10 parts water and you’ve got pretty good pickle. Cheap and effective.
– alonzo

[RickPowell]

Thank you so much!

Yeah the motorcyle battery version of it must be mostly water so thank you so much i’ll try it.

I’m not against buying actual jewelry profession supplies but I live on a barrier Island that doesn’t have Amazon vans, all packages take forever so I try to find local solutions by driving

[mrsples2]

Nancy thanks for researching this phenomenon. I have always wondered about it and couldnt find an answer anywhere. Its happened to me quite often.

[rmeixner]

Neil…You may be convincing me not to do a floor myself. We want to replace our 25 year old Pergo with something new. I don’t have a hard time with pickling my work. The crock pot heater gave out long ago, so I just use a cold solution of pH down and tap water and then rinse with tap water. I don’t usually pickle an annealed ingot until the last roll. Then I will sand and polish the sheet prior to cutting it up into whatever shape it will become. If there is a nasty stain or glassy flux on a piece once it is done, I put it in a small stainless steel pot with a very concentrated solution of pH down and water, place the pot on a tripod and, with my handy butane torch, boil the piece in the solution until it is clean. This will usually take just a minute or two and I like watching it go from stained to frosty white. That’s about it…Rob

[jeffg-moderator]

I’ll be surprised if motorcycle battery acid is a different concentration from car battery acid? But maybe it is? Car battery acid is 37% sulphuric acid.

Alonzo is mixing his drain cleaner sulphuric acid solution at 10-1. That is slightly less than 10% sulphuric acid. (that is a guess because he says the drain cleaner is close to full strength, but not full strength sulphuric acid).

I tried to find exact numbers, but couldn’t. But my memory is that Sparex Jewelers’ Pickle is mixed to a 3%-5% acid solution. This means that if you’re using 37% sulphuric battery acid, you have a very strong acid solution that has its own safety hazards.

Once you decide to not use a product, like an acid in a way that it’s not designed for you really need to make sure that you know what you’re doing with proper math and proper mixing procedures.

There’s a lot of beginners who read these threads so it’s very important with chemicals that we steer them in the safest direction. For me personally, I buy the smallest container of dry pickle that I can from a jewelry supply company and follow their mixing instructions exactly. Sure that’s a little bit more expensive, but not having the responsibility of excess acid to store and dispose of in my home studio is totally worth it.

Jeff

[RickPowell]

Maybe it is, but here in America, battery acid is really only sold to the public with the intention of old motorcycle style batteries. Or at least that is how Autozone and other places label it. Car batteries are sealed in USA so when the acid is sold to the public like at Auto Stores, it’s labeled as motorcycle battery acid because those some of those are still unsealed.

So we just call it motorcycle battery acid if you buy it in the public.

But as a car enthusiast, I do know that until the 1960’s, car batteries were sold unsealed and they would actually build/fill the battery when you bought it form the auto shop so it was fresh.

[wldlzrd1]

Hi,

ok, so!..possible solution- make the Pickle-it hotter…

I purchased the Pickle-It quite awhile ago, in the smallest size available, which was a 3lb box…sooooo even though it has been causing me grief, I figured I would use it until it is gone…but maybe I should bite the bullet…and try citric acid alone…

someone on the forum recently mentioned not using pickle, but rather just hot water…so i figured I would add that as a pre-pickle step to my pickle process and at least it would keep my pickle cleaner.
I have found that it cleans off all the flux nicely, but not all of the oxides.

(I had recently gotten a larger 3qt 6x8" oval crock pot for my pickle, to accomodate larger sheet strips, so I use my smaller 1.5qt 5.5" round crock pot, with hot water, set to high)

now, I should have thought about this sooner…(my brain started working when someone mentioned heating their pickle with a flame)…I have been using the “low” temp setting for my pickle, thinking that would be better and not reduce as fast…

yesterday i decided to set my pickle pot to “high”…and! voila! no grey stain in either the pickle or the baking soda neutralizing bath (the box does say that Pickle-It is safe for household drains…but I prefer to neutralize first…)

I googled crockpot tempuratures…the general consensus is low is 180-200, and high is 280-300…

water boils at approx 212 degrees farenheit…

perhaps my error was not setting the tempurature high enough…

I then went back to the Pickle-It box, and read the details, and lo and behold it says to “heat until boiling, maintaining a gentle boil”…

perhaps this is where the error of my ways lay…i was not getting solution not hot enough…?

maybe I will need to toggle the heat from low to high, for a few minutes, when I put something in the pot…

I shall report back if the dreaded grey stain returns!!

Julie

[RicardoA09331]

Hi, all. I have a PhD in biochemistry, and I have some thoughts.

From the Zeothix website:

“ZEOTHIX® 265 by Evonik is a rheology modifier based on micronized precipitated silica. It offers an excellent balance of flow out during application and excellent sag control for superior thin film coverage. Although it’s a fine powder, it is denser and easier to disperse than fumed silica.”

This is a flow and anti-caking agent for the Pickle-It powder (I assume it comes as a powder) and might be the culprit here. It does absolutely nothing in the pickling process, and in solution just amounts to tiny particles of silica suspended in the liquid. For all you know it might even be slightly abrasive.

As for the other stuff, I’ve never been sure what the salt is alleged to do. Citric acid alone is an electrolyte (makes the solution conductive) but that’s neither here nor there in terms of the pickling reaction. The bicarbonate is just adjusting the pH a little, making the solution fractionally less acidic (It will turn a little of the citric acid into sodium citrate) and helps hold the pH more constant (citric acid plus sodium citrate is an acidic buffer). What’s doing the pickling is the citric acid alone. I’ll add that sodium bisulfate is a “partially deactivated” form of sulfuric acid, meaning it will be less agressive than the acid but will last longer. Think of sulfuric acid as downing a shot of tequila versus bisulfate as sipping it. I use ‘food grade’ citric acid, about a tablespoon for two cups of water, mostly eyeballing it, and it works like a charm.

[jsfandskh]

Sparex is sodium acid sulfate or sodium bisulfate (same thing, different names)… NaHSO4… the old fashioned Saniflush was the same chemical, came as dry crystals, and was far cheaper than Sparex. It also worked identically. I used it exclusively as silver pickle until the formula was changed. Sulfuric acid is H2S04… it’s acidity is higher since there are two hydrogen ions that come off it in water, with the first hydrogen ion having a much higher pKa than the first, making it more acid than sodium acid sulfate. Sulfuric acid will also work well but the concentration has to be diluted to match the pH of a solution of sodium acid sulfate. A 1 molar solution of sodium acid sulfate has a pH of 1. A 1 molar solution of sulfuric acid has a pH of 0.3… to make one liter of 1 molar sulfuric acid, SLOWLY add 50 ml of concentrated (97-99% anhydrous sulfuric acid) to one liter of COLD distilled water…This is DANGEROUS!!! concentrated sulfuric acid if dumped into water will cause it to flash boil!..you can buy anhydrous sulfuric acid at chemical supply stores… this gives you a 5% solution. battery acid is typically stronger at 35%…, it is definitely more acidic than Sparex… more acidic solutions can be made out of sodium acid sulfate by just increasing the concentration, by adding more.
Sulfuric acid and NaHSO4 solutions don’t strongly attack iron, which is why they are used in toilet bowl cleaners. Muriatic acid which is impure hydrochloric acid does… it will burn stainless steel, leaving it blackened…Acids in general are frowned upon by professional plumbers because of the corrosion it causes to cast iron sewer pipes. Lye doesn’t attack iron but it cakes up and clogs pipes with grease that it doesn’t break down… Liquid Plumber with lye solution is the only lye product left on the household goods section of supermarkets.

Before I get off the topic: PLAIN sulfuric acid of high purity (reagent quality) and plain sodium acid sulfate which is much much safer than anhydrous (95-99%) sulfuric acid give you better results than added ingredients… I’ve never had problems with pickle discoloring silver with the old Saniflush…except when I accidentally “pinked” it (keep iron away from pickle!!) the addition of salt: NaCl will chloride pure silver surfaces. It’s a whitish discoloration that isn’t a problem since it spontaneously reverts back to pure silver upon heating…a fine gray coating after pickling is fine silver. The aluminum baking soda treatment for stained silverware leaves a coating of grey fine sliver that has to be polished with a soft cloth…a professional silver restorer warned against using that technique because it will eventual strip off thin silver plating by converting the plating to fine silver that gets polished off…
PLAIN citric acid has a pH of 3-5… a 50% solution has a pH of 1.8, which is fairly strong for an organic acid. It also is a mild reducing agent. Although weaker an acid, it’s much safer than either sodium acid sulfate or sulfuric acid which will burn your skin.
Vitamin C or ascorbic acid is another organic acid that also has a low pH at high concentrations and is also a mild reducing agent, stronger than citric acid for reduction… but it’s far too expensive to use as pickle…
Organic acids will gradually oxidize and lose their reducing ability…but they will become more acidic as the process takes place…as such they may lose some of their reducing pickling power with time.

Question is why pickle it when the ingot came out totally clean in the first place?..the baking soda treatment neutralized the acid but left behind but most likely deposited blotches of fine silver. That product doesn’t make sense to me… maybe the baking soda, sodium bicarbonate was added to adjust the pH of the citric acid. the small amount of iodized table salt would add chloride…the iodine is only in trace amounts and probably would not be in enough quantity to cause the gray discoloration after using baking soda.

After using the old Saniflush as an identical chemical as Sparex, I would use just pure sodium acid sulfate. Or if unavailable, sulfuric acid…both can be bought from a local chemical supply store without a license… It’s expensive, but will last for a long time, since you don’t need very much of it. the caveat with sulfuric acid is that battery acid has a lot of metal contaminants, as some of it’s recycled battery acid… Reagent grade is better but comes concentrated… always add acid to water, never water to acid… especially sulfuric acid… concentrated reagent grade sulfuric acid is anhydrous (no water in it) and will react violently to water, causing a steam flash back if not poured in very slowly and constantly mixed…the risk is getting splattered by acid…
One last word on acids: I have used both muriatic acid and reagent grade nitric acid. Muriatic acid is hydrochloric acid at 37%… it’s the maximum strength as no more HCL can be absorbed by water… as such, opening a bottle will release HCL fumes which are corrosive to lungs, eyes, and everything else… reagent grade HCL is clear, muriatic acid is yellow from ferrous iron… Nitric acid is so dangerous that I don’t recommend anyone using it… it fumes HNO3 gas when the bottle is opened. It reacts with metals to produce N02 which is a corrosive, toxic brown gas… any work done with it has to be done under a fume hood with an acid neutralizing filter or done outdoors…DO NOT breath any of the fumes…it will burn the lungs…
Final, final caveat: don’t EVER mix acid with bleach nor with strong alkalis, like ammonia or washing soda. The bleach will break down and exsolve a yellow green gas which is chlorine gas… corrosive and toxic… can’t breath it in without burning your lungs!!!
So much for the chemistry…

[jsfandskh]

thanks for the information on Zeothrix… I wrote my post before reading yours… I agree 100% with you.
I used NaHS04 in the form of Saniflush which worked just as well as the far more expensive Sparex…both are the same chemical… then Saniflush changed it’s formula…It don’t think that organic acids are aggressive enough…but sodium acid sulfate/sodium bisulfate worked fine for me…never tried anything else as the results were very good.

[jsfandskh]

I also have some background in biochemistry… but from a long time ago… I know this is irrelevant, but new biochemistry/molecular biology has be nothing short of revolutionary… it’s applicable to my area of medical specialty.

[aggie.p]

Sounds like we come from a similar background. My bio chem degree is over 35 years old. Another product that works or pickle, and is cheap s swimming pool acid. You buy it in gallon jugs. It’s Sodium bisulfate based formula.