Knob cleaning in bulk

[robin0577]

I'm currently refurbishing an old (almost vintage) sound desk. It has a total of 418 plastic knobs which need cleaning. Any suggestions for doing this in bulk? I fear doing them individually would lead to insanity, or at least more insanity than usual. There are no metal inserts or fixings to worry about, and the dirt appears to be just general "finger muck"

[mole42uk]

Put them in a cloth bag and run them through the dishwasher with a normal tablet. Don't use the highest temperature, some plastics are a bit sensitive!

[Nickthedentist]

I'd try ONE first!

[robin0577]

Thanks chaps, I don't have a dishwasher here but I should be able to use my mother's at the week end, I'll let you know how it goes...

[SurreyNick]

I read somewhere that a sand tumbler is also very effective. Basically a large rotating container partly filled with fine sand into which the objects to be cleaned are placed. I'm sure you get the idea.
Nick

[60 oldjohn]

Dish washer may be ok, BUT Not if there are any bright trims. Guess how I know.

John.

[paulsherwin]

Soaking them overnight in dilute bleach may work, but try a single one first in case the colour fades.

[Herald1360]

Ultrasonic bath?

[Bazz4CQJ]

I also think that an ultrasonic bath (using water and a selected detergent) would be the best approach and would be very wary of dishwashers and of bleach. For info on ultrasonic cleaning agents Google "Decon". If you really value these knobs, it would be best to use a progressive approach; lowish temperatures for a shortish duration (40'C for 15 minutes?) to begin with and repeat/increase as may be required. Dishwashers are to cleaning what blow-torches are to soldering (unless the component was specified at manufacture for dishwasher cleaning).

B

[ThePillenwerfer]

The best stuff I've found is oxygenating stain removing crystals. Vanish Oxy-Action is the famous one but I use the stuff from Poundland.

Just stick some in a bowl of hot water, drop the knobs in and stir then 'round and they'll be clean.

I did this with the key-tops off a filthy old computer keyboard and they were spotless in less time than it's taken me to type this.

- Joe

[davidw]

Joe's "oxy-action" method is how I did all the buttons from my juke box and it worked very well.

[Radio Wrangler]

HP routinely specified that PCB mounted components must withstand a dishwasher cycle using calgonite detergent. There were very few exceptions.

The flow soldering line bubbled acid flux over everything before it went through the pre-heater then the solder wave, there was a cool-down period and a hot rinse before boards got hit with strong jets of hot, detergent-laden water, then a final rinse. Trimmers and board mounted panel pots had to have good enough sealing. Switches had to be sealed, or to let the stuff wash through them without being trapped.

DIP switches and some makes of trimpots had a tear off sealing strip over their sliders and screwdriver slots. So dishwashing them again would need replacement tape stuck over them if they ever got washed again.

I'd dishwash one knob as Nick suggested, just to make sure that marker lines don't lose their paint filling. We used to ship fabulously expensive precision test equipment where every electronic part had met an industrial dishwasher.

David

[RF Burn]

A twenty minute soak in a warm solution of normal household detergent is my cleaning method of choice, it seems to 'lift off' most dirt and clean up surface stains. Do not use this method for valves though unless you want to remove the markings (and that includes the so-called "acid etch code" which is actually an ink stamp).

As with any cleaning method - on cherished vintage parts test a small area first.

[G6Tanuki]

I find soaking in a strong solution [a teaspoonful in a cup of medium-warm water] of 'bio' clothes-washing liquid overnight works well to lift the grime off ribbed/knurled knobs: a going-over with an old toothbrush in the morning and they come up clean and bright.

For cleaning knurled solid-metal knobs I'm told that "Steradent" tablets are effective.

[PSValves]

I'd use ultrasound with a warm, mild detergent solution. I've been using ultrasonic cleaning at work for the last decade or so, on all manner of delicate plastic and metal parts and had very few problems. The big advantage is that you can use a far milder detergent and get the same end result as a much more aggressive solution. U/sound is extremely popular with jewellers for this reason.

N.B. Some plastics, like old acetate, lose their sheen after cleaning and may take on a matte finish. A quick polish usually brings them back up to perfect condition.

[robin0577]

Well, the dishwasher worked a treat, although I wouldn't risk it on delicate vintage stuff or knobs with painted on pointers. These were late '80s - early '90s two colour plastic mouldings, and fairly robust.

[tracypaper]

A bit of Persil in warm water and an old toothbrush works for me, not just the knobs either
all plastic parts off record decks as well, Then again I haven't got 418 to do.
Vanish Oxy sounds like a plan, brought my speaker cloth up a treat.
Gaz.

[stevehertz]

I too use an ultrasonic cleaner containing warm water and a hint of washing up liquid. I sometimes find that after cleaning, the knobs may need the use of a toothbrush to remove any remaining 'chicken fat' in grooves etc. But the offending material has been loosened by the ultrasonic process and comes away easily. Ultrasonic cleaners are not expensive and quickly 'pay for themselves'. I got mine from Aldi for something like £20.

Otherwise, fill a plastic washing up bowl with hot water and plenty of washing up liquid and leave the knobs to soak overnight. They will then need to be individually brushed with a toothbrush to get them clean. Rinse thoroughly and dry quickly using a hair dryer to avoid any fixing screws rusting. I wouldn't use bleach as it may 'bleach' the surface of knobs that have roughened with age.