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Sprays foam that removes Camo and Regrow and pops Lead Bloons.
~ In-game description

Cleansing Foam is the 3rd upgrade of Path 2 for the Engineer Monkey in Bloons TD 6. It grants the Engineer Monkey with an independently shooting cleansing foam gun that regularly sprays cleansing foam around the Engineer's range every 2.0s (every 1.2s with 2-3-0). The foam blobs can remove the camo and regen properties from bloons that touch it, including from DDTs. They also damage Lead Bloons by cleansing them, converting normal Leads and Fortified Leads into Black Bloons, but zero damage to DDTs. Each foam blob can soak up to 10 bloons (15 with 0-3-1 or 0-3-2) or 8.5s before disappearing, whichever comes first.

Starting from Version 29.0, Cleansing Foam's foam will default on Close and can be retargeted to any valid location within the Engineer's immediate range, including on non-track locations.

Crosspaths greatly affect Cleansing Foam's supporting role. Sentries with Cleansing Foam cause each hit to strip Camo and Regrow as well as cleanse Leads in a similar way to normal foam. With Pin, affected non-blimp bloons passing the foam are briefly slowed down by 50% for 2 seconds.

It costs $720 on Easy, $850 on Medium, $920 on Hard, and $1020 on Impoppable.



Cleansing Foam adds a large blue tank of foam with a white band and grey tubing linking it to the nail gun, which now has blue highlights and spurts foam as well. The Engineer's helmet is painted white, and their jacket is also swapped out for a white lab coat.

Crosspathing with path 1 paints the nail gun green and gives Engineer a combination wrench, before painting its handle red.

Crosspathing with path 3 paints the back of the helmet black and adds a grey extension to the nozzle, before painting the entire helmet black and granting a pair of orange and black work gloves.


Cleansing Foam adds a new foam attack to the Engineer, deploying foam capable of cleansing Bloons which pass over it, stripping them of camo and regrowth properties, and converting leads to Black Bloons. This foam is deployed every 2 seconds (every 1.2s with Faster Engineering) and has 10 pierce, (15 with Oversize Nails) and a lifespan of 8.5 seconds.

Foam pierce can be consumed by Bloons without any special properties.

The foam naturally targets Close, but can be selectively targeted anywhere within the Engineer's range.

Sentries obtained from 1-3-0 remove properties with their projectiles, on top of the increased MOAB and Fortified damage from Deconstruction. 2-3-0 increases rate of deploying sentries and creating foam.

Foam gains +5 pierce from Oversize Nails, for a total of 15, and is able to slow non-blimp bloons by 50% for 2 seconds when given Pin.



Cleansing Foam fulfills a similar role to its BTD5 counterpart, removing Camo and Regrow properties off bloons hit by the foam globs. The difference, however, is that Cleansing Foam now comes with large range already and targets consistently on a given location. It is not necessary to the Engineer away from the track, as the Foam can be smartly targeted to any desired location within range. Path 1 crosspath not only provides the Engineer with needed extra sources of popping power, it also enhances the production speed of foam globs by a significant amount with Faster Engineering, at a +66% increase, compared to Path 3 with just gives pierce.

Version 31.0 has reworked Cleansing Foam to achieve much stronger crosspathing value. In particular, 0-3-2 can be used to slow down all regular bloons, making the pierce consumption of foam not become a liability but rather beneficial. It is a very cheap slowdown option, and can compete against regular glue.


  • Crosspaths are very influential for Cleansing Foam but is not vital. Giving crosspaths can greatly assists the power of foam.
    • 2-3-0 Cleansing Foam increases DPS from the Sentries plus much faster reload of the foam attacks. In fact, the attack speed of foam increases by +66% compared to just +50% (or around 38% with Thicker Foams) pierce from the opposite 0-3-1 (or 0-3-2) crosspath.
    • Crosspath choice has now changed drastically after Version 31.0: Thanks to foam's ability to briefly slow bloons, 0-3-2 is now significantly more effective. This may even be true in spite of the fact that sentries, starting from version 31.0, also remove special properties.
  • Remember that the foam attacks from Cleansing Foam can ignore Line of Sight, so it might be worth considering this in specific situations.
  • With the Monkey Knowledge "Thicker Foams", the cleansing foam's pierce increases by 3.
  • Cleansing Foam will take the camo off DDTs, making this one of the cheapest ways to allow towers to attack DDTs.
  • Cleansing Foam does not damage DDTs, despite dealing damage to normal Leads. This can be useful for All Pops CHIMPS challenges when using Overclock.
  • One can target Foam away from the track to intentionally decamo DDTs and not waste so much pierce on regular bloons.
  • Note that sentries from Cleansing Foam can't necessarily detect Camo Bloons, meaning they can't necessarily apply the decamo to them unless given Radar Scanner or similar camo detection. However, they can still always degrow Regrow Bloons and cleanse Leads.



None (so far)

  • [31.0] There was formerly a bug where Cleansing Foam could slow down all MOAB-class bloons including BADs. It also included Bosses but was never possible without use of hacking to manually include Bosses, as they are only available legitimately through Boss Events, and the only available Boss Event at the time banned Engineer Monkey. Bug patched in 31.1.

Version History[]

Power of non-crosspathed Cleansing Foam remains similar, but the Version 21.0 crosspath buffs improved viability of this upgrade overall.

Engineer is quite poor in terms of crosspathing, so we've added crosspath benefits to Cleansing Foam as well as an overall price buff to the middle crosspathing upgrades. [...]
~ Ninja Kiwi
  • Buff 2-3-0 Cleansing Foam now has increased attack speed (2.0s → 1.2s).
  • Buff 0-3-1 Cleansing Foam now has more pierce (10 → 15).
Engineer's bottom 2 paths have a heavier support focus, so to start them off a bit easier we have shifted some starting cost out and into the non-supportive path. For the sake of further improved crosspath potential, we have also re-envisioned the 'Larger Service' crosspath as giving smarter service as well in the form for targeting for Bloontrap & Cleansing Foam
~ Ninja Kiwi, referring to both lower base Engi cost and smarter on-track contraptions
  • Buff Cleansing Foam now defaults to Close instead of randomly placed
  • Buff Cleansing Foam now gains an extra targeting option to force foam to be placed on any track section in the Engineer's range.
[...] Cleansing Foam has had some extra crosspath utility added at the cost of a small price increase and a large decrease to Ultraboost price.
~ Ninja Kiwi
  • Nerf Cleansing Foam price increased ($800 → $850)
  • Buff Cleansing Foam now also directly incorporates the attacks gained by crosspathing it.
    • Buff Foam makes Sentries shoot Foamy nails that strip properties
    • Buff Pin allows Cleansing Foam to slow Bloons 50% briefly. Also includes MOAB-class bloons.
      • Buff [undocumented bug] Also slows down BADs
032 Engineer Cleansing Foam now works correctly on all MOAB Class targets - hope you enjoyed that temporary treat
~ Ninja Kiwi, cheekily referring to the MOAB-class slowdown bug
  • Nerf 0-3-2 Cleansing Foam no longer slows MOAB-class bloons

Description changes[]

  • Change Description changed from "[...] Regrow and Camo [...]" to "[...] Camo and Regrow [...]".


When deploying Cleansing Foam:


0-3-2 Foam Bug[]

Official artwork[]




  • In BTD6, there is a specific glob-dispensing sound for Cleansing Foam placement. In BTD5 generation games, there was no specific sound for them. Additionally, foam globs are dispensed near-immediately onto the track upon spawning from the Engineer, rather than projectile-based like Spike Factory spikes as the foam globs were in BTD5.
  • Froth flotation is a process used to separate hydrophobic materials (e.g. most carbon compounds, which aren't soluble in water) and hydrophilic materials. Foamy substances like this are used for removing heavy metals like lead and mercury. Rubber is hydrophobic, which means it shouldn't be affected by froth flotation. It could suggest that Cleansing Foam is actually made of a solvent used to perform froth flotation.
    • Foam is a by-product of frothing, further proving the theory that Cleansing Foam is made of a foamy solvent for froth flotation.
  • There exists a real-world product called "cleansing foam", but this is not the same thing as Cleansing Foam in Bloons TD 6, which is designed to instantly corrode Lead Bloons and permanently remove Camo and Regrow. The real-world generic product "cleansing foam", also known as "foaming cleanser", is a cleanser designed to protect skin, primarily to remove dirt and impurities from skin pores without ruining natural skin oil. It is mainly used on the face due to its more gentle nature compared to conventional soaps.