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For the BTD5 counterpart, see Cleansing Foam (BTD5).
Sprays foam that removes Camo and Regrow and pops Lead Bloons.
~ Upgrade description in BTD6.

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 track 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. 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.

It costs $680 on Easy, $800 on Medium, $865 on Hard, and $960 on Impoppable.



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, severely decreasing its accuracy due to larger random spread. Placing it far away from the track can help its reliability overall, but using the 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, so it doesn't have to be placed far from the track anyway.


  • Use 2-3-0 Cleansing Foam for the added 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% pierce from the opposite 0-3-1 (or 0-3-2) crosspath.
  • 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.

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).

Description changes[]

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


When deploying Cleansing Foam:

  • [foam bubbling]
  • [foam bubbling]
  • [foam bubbling]
  • [foam bubbling]


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.