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Cleaning Small parts prior to blackening

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I just received a bunch of brass belaying pins to replace my kit parts. Now I have to clean them up to either paint them or blacken them. I know I can put them in my Dremmel or drill motor and spin them against some fine emery cloth, scotch brite or even a file but I am looking for a more efficient way as I have close to 50. I have a bullet tumbler in my garage that has sat unused for many years (too many) and am thinking of using that. My thought is thoroughly clean the bowl out to remove any polishing compound then replace the corncob media with fresh clean #60 sand from our our sand blaster at work and then tumble away for a couple of days. After that I would soak in vinegar and then then a good scrub with soap and water or an ultrasonic cleaner before blackening. rinsing with distilled water first of course.

If this works it would be great for cleaning things like eye bolts, hooks etc as I have had inconsistent results blackening small parts like this.

My question, has anybody tried this? Am I wasting my time? Any other thoughts about batch cleaning of small parts?

 

Sam

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Sounds like a lot of trouble to me.  For those bits, my standard recipe is:  Wash in dish soap, rinse well and let dry.  Put into white vinegar for maybe 30 minutes or so, rinse with water, and allow to dry.  Vinyl gloves are must to keep oils off the brass.  Then, blacken.

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I have tried several processes successfully but I have now settled on a more efficient way having purchased a small ultrasonic cleaner.  I use Birchwood Casey (diluted) as the blackening agent.  Always rinse and buff with a soft cloth or towel paper on completion and redip in blackener if required.  As Mark points out rubber gloves when handling , then cotton gloves after blackening (until buffed and you are happy with the finish, as handling is usually not a problem for me after the item has been blackened and buffed.  I use cotton once blackened until buffed as i found the rubber tends to grip the item too much making it harder to manipulate.   

 

Method 1:  wash and rinse, soak in vinegar and rinse, soak in a weak acid solution and rinse then blacken and rinse again.  I use a tea strainer (dipping type that closes which allows me to swish all the items around in the solutions.  The acid can be diluted nitric, or muriatic (brickies acid) or even acetone.  I only soak in each solution for about 15 mins and vigorously agitate quite often; but a longer soak if you have the time can create a better finish first up..

Method 2:  (a little more time intensive) first I use a fibre bristle-pen to 'scratch' clean the entire surface of each item.  I find this necessary on some after-market parts (especially K&S brass shapes) as they seem to be treated with some sort of finish - then as for method 1.  This takes more time but usually yields an acceptable finish on the first attempt.  be careful with the fibres from the pen (fibreglass) as the very small 'dust/pieces' are a real pain to get out of your fingers if they stick in :) 

 

Method 3:  (if you have an ultrasonic cleaner - small ones are pretty cheap these days).   Almost the same as for method 1 or 2 (depending on the type of brass i am blackening) but instead of a prewash in warm water and detergent I use the ultrasonic cleaner - a lot faster and better clean.  With some trials I was able to blacken with very acceptable finishes without the vinegar and/or acid soak afterwards.

 

I have settled on using the fibre-pen and ultrasonic wash before blackening on all my pieces now unless it is a very (very) small part made from soft brass - the extra time in using the fibre-pen results in a lot less rework.

 

I hope this provides some help in choosing a method suited to your needs; cheers

 

Pat

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Mark, Pat, thanks.

I have a small ultrasonic cleaner from Harbor Freight. I have been using it on hooks and eyebolts but assumed I needed to scuff the surface first with a file or fine sand paper. Am I reading correctly I don't need to do that with a ultrasonic cleaner? That's encouraging, it was why I considered the tumbler and sand in the first place. I will try that before I go to all the extra effort.

Sam

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Sam, I finally had success blackening with a good finish after rinsing the parts well in alcohol to clean and remove any finger oils, and then leaving the parts in vinegar for 30 min or so. You have to do two things- generally clean the parts, and remove the oxide layer so the blackener works.

 

You could just use your ultrasonic cleaner for the cleaning part, and use vinegar to remove the oxide layer. I also had better luck dabbing the blackener on with a q-tip and periodically rinsing it off in water rather than dipping the parts in, as nonsensical as that may be.

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Mark, I might try that. I need to find out what is in the powder that came with the cleaner first.

 

Vossie, I have been doing something similar; dropping the parts in a small amount of agent letting them sit for a few minutes and agitating regularly, taking them out rinsing them off in distilled water. After they dry a quick buff with a clean dry cloth for camera lenses. back in they go for two or three cycles.

 

Roger, that might be something to try at some point. Although I see Murphy hiding behind me with a little hand card reading "Watch this guy demonstrate the Bernoulli Effect!!" 😂 Murphy thinks he and I are good pals.

 

Most of the parts I have had issues have been parts made from K&S brass. Even after annealing and a good scrub with a maroon scotch bright pad I have had inconstant results. After reading Pats comment I think those issues might be related to the brass itself. I don't know. It sounds like I don't need to try the tumbler though from what I am hearing. That's good, I have enough other things to keep me busy without adding more steps to the process.

 

Sam

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Have you tried soaking the parts in acetone or lacquer thinner?  Unlike varnishes that cure, even after it has dried lacquer dissolves in acetone.  Lacquer based coatings are popular with manufacturers due to their quick drying time.  If K&S gave their brass a quick coating of lacquer, acetone should work.  Acetone is toxic and gives off a smell that does not appeal to other members of the household.  I keep a supply of very small containers on hand so that I can use very small quantities.  If K&S is using some sort of water based coating to comply with VOC rules then using the air eraser to clean the raw material before fabricating your parts should work.

 

Roger

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Roger,

Never thought of acetone as I assumed the annealing process would burn it off. We have many gallons of the stuff at work as well as other chemicals not available to the general public.

As an aside acetone, at least in California, is not considered a VOC. I understand chemically it is but legally it is not. One of the automotive finishes we work with is considered "zero VOC" although as I understand it acetone is a main ingredient, go figure!!

Sam

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Hi Sam, to answer your earlier question - depends :)  - sorry.  If it is one of those products with the protective/finish coat on them I still use the fibre-glass scratch pen; but, the ultrasonic cleaner has certainly reduced the number of times I have to use the pen.

 

cheers

 

Pat

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Hi everyone. Try use water with citric acid. It cleans all the oils and grease off of parts to be blackened. Immerse parts in the solution for about 10 - 15 min, simmer from time to time, rinse with clean water, let it dry and you are good to go with blackening. Use disposable gloves or try not to touch the parts with bare hands. I get perfect results every time.

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18 hours ago, src said:

Vossie, I have been doing something similar; dropping the parts in a small amount of agent letting them sit for a few minutes and agitating regularly, taking them out rinsing them off in distilled water.

Yeah, that's what I did at first too, as it's logical. I'm just saying I've actually gotten better results by dabbing it on by q tip, doesn't make any sense but it has consistently done better than dipping.

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I use Sparex #2 heated in a small crock pot for cleaning anything I will blacken - using Birchwood Casey Brass Black.  Heated Sparex works great on cleaning up soldered parts - but if there is a big build up of crud from the soldering I often use the fiberglass etching pen before the Sparex.  After about 10 minutes in the heated Sparex I rinse the parts in water, then a rinse in Acetone that is then rinsed again with distilled water and then air dried.

 

I routinely blacken brass eye bolts.  I had issues with them not blackening consistently.  Brass w/o a coating of some sort will dull and darken so with all brass eye bolts being shiny I concluded they are coated.  I lay them out on my fire block at my silver soldering table and hit them with the mini torch and then clean in Sparex as above.  Doing this makes sure they all blacken nicely.  As any brass shapes (K&S type) that I blacken have been soldered - the coating is burned off and treating in the Sparex as above assures even blackening.

 

Sparex should not be boiled!  The crock pot can't boil water so it's a good way to heat the Sparex.  Jeweler's supply places sell these little crock pots for $35 or so but I have found several at Goodwill  or other similar places for less than $5.  I have some on hand as replacements but have supplied local club members with them also.

 

As Sparex is acid based the parts are thoroughly cleaned and etched in one step.  Sparex is available from Jeweler's supply places and welding shops.  Don't use metal baskets or tweezers to hold the parts as the continued use in Sparex will eat them away - plastic tea strainers work great. 

 

Jeweler's supply place sell copper tweezers to take pieces in and out as the use of metal can cause a build up of metal in the fluid that can coat the pieces and interfere with plating the parts.  As I do plating too I stay away from the metal tweezers and baskets.  Never had a problem with blackening parts when I previously used metal baskets and tweezers in the Sparex but after investigating plating and being forewarned about the use of metal in the Sparex  I just use the plastic baskets and copper pliers all the time.

 

Kurt

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I will take a look at both the Sparex and citric acid. I have a small min crock pot laying about somewhere. Citric acid shouldn't be too hard to find, even in California. There used to be a place near where I live called TRi S Sciences, they sold very small quantities of most any chemical you could think of to students. Sadly they went out of business some time ago.

 

Are these the fiberglass etching pens mentioned above?

353351605_ScreenShot2019-04-21at9_07_31AM.thumb.png.4c461c197b9a4a3f3dc49a9caf6cea04.png

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I agree that Sparex works extremely well.  Soldering pastes, pickling materials, and other items for small metal work can be found in many places, but Contenti has been my go to place for a long time.   The pickling powder can be had for $5 for a 2.5 pound bag that will last a lifetime in this hobby of ours.   I am not involved with them in any way other than beng a happy customer.

 

Allan

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Hello Sam,

 

I agree with mtaylor about lot of work for a few small pieces.  Also, those etching brushes you showed are an excellent choice.  I've always preferred the glass fiber brushes, they're exceptionally suited for this task.  Brass brushes tend to clutter up easily, and also offer a small amount of particles which negate previous steps.

 

Here's the deal.  The very small metal parts show many smooth surface areas if you look at these under magnification.  Brushing the small surfaces with a light, abrasive "pencil tool" will slightly roughen up the surface, and this procedure will help the blackening agent to better grip.  Even if you choose to paint, same positive effect.

 

I'd suggest just lay the parts on a glass slab, and spray them automotive brake cleaner.  Dry the rest, dump them in alcohol, you're ready to go.  Air drying will proceed quickly.

 

I'm a retired master hand craftsman of the watchmaker branch.  We do this stuff and related, on a fairly regular basis.  Metal prep is a must, but doing too much too often is a waste of time.  We want best results without unnecessary events.

 

Good luck to you, sir.  I'm happy that you give small things such great attention.

 

Michael

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