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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 a foam placement attack that regularly sprays cleansing foam on a particular spot within the Engineer's range every 2.0s (1.2s with 2-3-0). The foam blobs can remove the camo and regrow properties from bloons that touch it, and converting normal Leads and Fortified Leads into Black Bloons. The foam disappears after cleansing 10 bloons (15 with 0-3-1 or 0-3-2), or after 8.5s have passed. The on-track foam will default to Close and can be retargeted to any valid location within the Engineer's immediate range, including on non-track locations. In addition, all attacks gain quadrupled attack speed for 1 second every start of each round, similarly to Smart Spikes.

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, though the sentries themselves still need direct camo detection. With Pin, affected non-blimp bloons passing the foam are briefly slowed down by 50% for 2 seconds.

This upgrade costs $765 on Easy, $900 on Medium, $970 on Hard, and $1,080 on Impoppable.



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Cleansing Foam

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 its jacket is also swapped out for a white lab coat. In the upgrade portrait, he is smiling cheerfuly as well.

Crosspathing with path 1 follows the paths for Sentry Gun and Faster Engineering. With the first upgrade, it paints the nail gun green and gives Engineer a combination wrench. The second upgrade paints its handle red and gives the distinctive green chevron on his helmet.

Crosspathing with path 3 follows the paths for Oversize Nails and Pin. The first upgrade paints the back of the helmet black and adds a grey extension to the nozzle. The second upgrade paints entire helmet black and granting a pair of orange and black work gloves.

The foam produced from the gun is white and bubbly, resembling white liquid soap that has foamed. When shot out, the gun emits a bubbly noise, much like the sound effect for the formation of suds.

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.

Targeting Priorities[]

Cleansing Foam targets bloons using the standard targeting priorities. It shoots straight movement projectiles.

  • First: Targets the first bloon visible within its range.
  • Last: Targets the last bloon visible within its range.
  • Close: Targets the closest bloon visible within its range.
  • Strong: Targets the strongest bloon visible within its range.

Cleansing Foam's foam utilizes Manual Targeting to deploy at a single spot within the tower's immediate range, and defaults to Close.


Updated as of Version 43.0. Listed prices exclude external buffs, any sacrifices, and Monkey Knowledge.
[Module | Data] Purchase Sell
Costs Easy Medium Hard Impoppable Easy Medium Hard Impoppable
Upgrade (X-3-X) $765 $900 $970 $1,080 -
Total (0-3-0) $1,565 $1,850 $2,000 $2,220 $1,096 $1,295 $1,400 $1,554
Crosspath (1-3-0) $1,990 $2,350 $2,540 $2,820 $1,393 $1,645 $1,778 $1,974
Crosspath (2-3-0) $2,330 $2,750 $2,970 $3,300 $1,631 $1,925 $2,079 $2,310
Crosspath (0-3-1) $1,945 $2,300 $2,485 $2,760 $1,362 $1,610 $1,740 $1,932
Crosspath (0-3-2) $2,130 $2,520 $2,720 $3,025 $1,491 $1,764 $1,904 $2,118

This upgrade's prices (or included crosspath's prices) are affected by the following MK: BetterSellDealsIcon Better Sell Deals



Cleansing Foam fulfills a similar role to its BTD5 counterpart, removing Camo and Regrow properties off bloons crossing the foam globs. The difference, however, is that Cleansing Foam now comes with large range already and targets consistently on a given location. 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 increases 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, becoming a very cheap slowdown option that 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. 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 ThickerFoamsIcon Thicker Foams MK, the Cleansing Foam's pierce increases by 3.
  • Cleansing Foam will decamo DDTs, making this one of the cheapest decamo options.
  • 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 cannot necessarily detect Camo Bloons, meaning they cannot 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.
  • Be careful when using Cleansing Foam in combination with towers that do bonus damage to camo bloons, such as x-2-x Monkey Ace, x-1-x Sniper Monkey, or level 19 See Invisibility Potion, as removing the camo property will cause them to lose the bonus damage as well. This can be especially important late game when trying to pop DDTs and their fortified variants.


  • [33.0] Engineer's start of round boost affects deploy rate of sentries and the main gun attack.
  • [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.
  • [32.0] Cleansing foam slow stacked additively on the same target, permanently locking down normal bloons, including Super Ceramics, if there is foam on the track. Bug patched in 32.1.

Version History[]

Balance Changes[]

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
  • BUFF [Undocumented bug] 032 Cleansing Foam's slow can stack on the same target, permanently locking them in place.
  • NERF Engineer's 032 Cleansing Foam slow no longer stacks on a single target
[...] Cleansing Foam is only seeing a slight tweak to help it be more viable if you want to attempt it as 'main camo detection’, and this mainly fixes some issues in ABR games allowing it to catch quick initial camo spawns.
~ Ninja Kiwi
  • BUFF Cleansing Foam attack now gains 1s of 4x rate on round start
    • BUFF [Undocumented bug] Also works for all other attacks (sentries and main gun)
  • BUFF Affected by 1-2-0 Deconstruction buffs to sentries
While better than many options, base Engineer still takes a lot of available starting cash so the cost is reduced slightly and being moved back up into Cleansing Foam & Bloontrap; also with a reduction to Double Gun’s price to reflect the lower value of the base tower. [...]
~ Ninja Kiwi
  • NERF Cleansing Foam cost increased from $850 to $900
    • Total price adjustment is $0 due to base Engineer Monkey (-$50)

Bug Fixes and General Changes[]

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

Extra Notes (Version History)[]


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 is 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 are not 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.