I recently was offered “a box” of unwanted LEGO for the price of showing up to haul it away. I was expecting perhaps a large shoebox full. After the hauling was done, I was pleasantly surprised to discover that (once all the moldering, spider-infested cardboard boxes were disposed of) the entire haul filled a 14 gallon Rubbermaid container.

What I was unpleasantly surprised to discover was that the previous owner had played with the bricks in the mud. Many, if not a majority, of the bricks had dried mud, dead insects, or other organic debris jammed up inside. This raised the question of how best to wash all these nasty LEGO pieces. There were many suggestions and recommendations available over the Internet. What was I to do? Why, use science, of course.

Spray

My first experiment was to place the pieces into a strainer and simply spray with water until clean. This method would probably have worked better if my kitchen sink were equipped with one of those hand-held rinse nozzles. Otherwise, showering tapwater over nasty bricks does not appear to be very effective.

Wash and Rinse in Strainer

For this experiment, I placed a strainer full of dirty LEGO pieces into a bucket of warm soapy water. Agitate the pieces for a minute or two, then remove strainer and rinse under running water. This method is easy, but hardly effective against anything but the least tenacious of surface soil.

Soak and Rinse in Strainer

This is the same method as above, with an extended soaking period before agitation. It is hardly more effective than the Wash and Rinse.

Multiple Soaks with Agitation

One recommendation was to repeatedly soak all the pieces in warm water and dish detergent, stirring occasionally, and periodically rinsing the pieces and replacing the soak water until it remains clear after stirring. I found this to be only a little more effective than the single soak method listed above. There was still gunk inside the bricks.

Multiple Soaks in Laundry Detergent

Another popular recommendation was to place the dirty LEGO bricks into a pillowcase, close it securely, and throw the pillowcase into the washing machine. Since I must use a shared laundry, I didn’t think it a wise method, should the pillowcase somehow open during the wash cycle. However, it occurred to me that the laundry detergent itself might be the secret ingredient. So for my next experiment, I tried the multiple soak method with laundry detergent. Laundry detergent was hardly more effective than dish detergent, and left a whitish residue on some of the bricks.

Soak and Scrub with Kitchen Brush

After soaking the next batch of pieces in a bucket of warm water and dish detergent, I scrubbed each of them with a kitchen brush. The kitchen brush is partially effective as it will remove much of the gunk from LEGO plates, but not from the little pits inside the studs. The kitchen brush removed almost nothing from inside the bricks.

Soak and Scrub with Toothbrush

The results were much the same as with the kitchen brush, though the smaller size of the toothbrush made it easier to clean the smaller parts. This was another partially effective, if tedious, method, of cleaning plates and other small LEGO parts.

WaterPik

In this experiment, I used a WaterPik dental water jet loaded with plain warm water as the scrub/rinse stage. This was very effective, blasting the mud out of the bricks. It was also messy, with clouds of flying water droplets everywhere. However, placing the both the tip of the device and the dirty brick underwater minimized the water storm. The only problem with this method is that the model of WaterPik I used was loud and only held enough water to clean a few bricks at a time.

Ultrasonic Cleaner

In this experiment, I used a 2.5 liter ultrasonic cleaning machine. I’m not sure how much of the cleaning observed was due to the ultrasound and how much was due to the heated soak feature. The machine did not remove all of the mud from inside the bricks. Perhaps using the proper cleaning solution would have helped.

Damp Washcloth

The most obvious method. It worked well enough to clean the outsides of bricks, but could not clean the inside of most of them. I thought this method was best suited for careful cleaning of pieces bearing stickers.

I also heard that the dishwasher could be used to clean a pillowcase full of LEGO pieces just like a washing machine could. I didn’t try this method, as I doubted that the water spray would be very effective through a pillowcase, and I heard that high temperatures could warp the bricks, and I also didn’t want to have to explain how I broke the dishwasher if the pillowcase were to open during the wash cycle.

My conclusion is that the most effective method for cleaning very dirty LEGO plates is a warm water soak with dish detergent, followed by a scrub with a kitchen brush or toothbrush. For cleaning very dirty LEGO bricks, I recommend the same detergent soak, followed by WaterPik cleaning of the inside.