I have a LEGO collection consisting of a number of rarer sets such as the monorail and 9V train sets.

I want to clean the pieces but I am curious if cleaning the parts affects their value? I plan on putting a few drops of dish soap in a laundry tub with warm water, gently mixing the pieces around, and then rinsing them off and letting them air dry. I obviously wouldn't do this with any 9V pieces or pieces with decals.

I know cleaning coins greatly decreases their value because it lightly scratches the surface of the coin. Should I be concerned with cleaning LEGO parts?

  • 2
    As you can expect, the answer to this will most certainly be "yes" in most cases as there's always a chance of scratching the parts. However, you could argue that getting bricks dirty is what diminishes their value to start with (some would go as far as saying opening the box is already a bad idea :-))
    – Joubarc
    Commented Jan 9, 2014 at 7:13

2 Answers 2


Cleaning coins reduces their value because being metal they form a natural patina with age. The patina is an indication of the coin's age, and supports its authenticity. Removing any of the patina through cleaning reduces the value because it removes this sign of its authenticity.

Cleaning LEGO pieces does not affect their value in the same way it does coins. It is generally accepted that used pieces will have some small scratches and will have lost some of the shine of new pieces. Unless the scratches are deep enough to be seen easily or the piece is damaged, these incidental small scratches have little effect on the value of used pieces or sets.

LEGO pieces do not scratch one another, although they may cause scuffs (which can be removed). Scratches are caused by substances that are harder than the ABS plastic LEGO pieces are made from. This is usually dirt and dust that contain small particles of grit. This can settle on the pieces and scratch them as they are handled. Many pieces are played with on the floor, where they pick up grit and can be rubbed into carpet or flooring that contains abrasive particles.

Cleaning them can remove this abrasive grit and reduce further scratching, but aggressive rubbing can cause more scratching. When I clean pieces, I like to let them soak in warm water and mild soap for several hours - overnight usually - with no scrubbing and just a gentle mixing around of the pieces. Then I drain the water and rinse them until there are no soap suds and spread them out in a single layer on a clean towel to air dry. This will get all but the most dirty pieces clean.

For pieces that are very dusty, I will soak them then run them under a tap and use the water pressure to clean off as much dust as possible.

For pieces with dried-on dirt or other substances, you need to scrape it off with something softer than the plastic, like a fingernail, or try using the thin edge of a brick separator which is the same type of plastic.


It depends very much on how you clean them, and why.

Parts that were covered in mud or excrement will have lower value after that regardless of how you clean them, but I suggest it's not the cleaning that is the cause. Similarly for parts exposed to cigarette smoke or other toxic substances. If you check Bricklink, for example, many sellers of second hard parts say "smokefree household" as an advertising claim.

Careful cleaning with things that don't damage the Lego would normally increase the value, but not enough to cover the cost of doing it (otherwise more online sellers would say "all parts washed before sale"). Most Lego is kept pretty clean, except for smoke damage as noted above.

I have preciously sold Lego that I bought in a big, foul-smelling bin after washing it to remove the smell. The smell was slight rancid, slightly just "house that is never cleaned" musty/mouldy. So I used laundry detergent and warm water, soaking and agitating over a day or so, then rinsed a couple of times and dried in the shade. The smell disappeared, I sold most of the bricks (I bought the lot for some specific parts). I removed all the transparent parts before cleaning, and carefully hand-washed each transparent part specifically to avoid visible scratches. But the scratches from the general washing seem likely to be less than the scratches from normal keeping Lego in a big bin and carrying that around. I didn't see any obvious new damage, at least.

I suspect but have not tried that machine washing would cause more damage. Bag washing in a dishwasher or washing machine will involve more agitation and possibly hotter water than the hand-washing I've done. If I was going to do this I'd try it first on a bag of low-value Lego. AFOL groups often have a supply of very low-value bricks from people who regularly buy bulk lots of second hand Lego, so it would be worth asking around for how they clean it or whether they'd be willing to donate some bricks for your experiments.

I have heard of people deliberately using reactive chemicals to "clean" bricks in a damaging way. Normally this is done with old white Lego that has yellowed with age. Oxygen free radical cleaners will restore the whiteness, but make the Lego brittle. Doing that would definitely lower the value of the Lego.

I am assuming here that everyone involved is honest - obviously if you do use harsh cleaners but don't tell buyers that's not going to affect the value until the buyers discover the problem, and then only if they have some way of telling future buyers about your actions.

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