White Hot Spikes is the 3rd upgrade in BTD4 and the 2nd upgrade of path 1 for the Spike Factory in BTD5. It costs $300/$350/$380 in BTD4. It costs $765/$900/$970/$1080 in BTD5. It enables the spike factory to pop Lead Bloons and with its road spikes. They can also pop frozen bloons if the Spike Factory is near an Ice Tower . The spikes turn red at their tips. The ability to pop leads only requires the first tack to break through the lead layer and thus, puts the lead-popping ability of the other tacks in the spike into waste. It is recommended to get the first two upgrades of path 2 before getting this one. It is usually useless to get this upgrade, except if you're going for a Spiked Ball Factory, or if you're fighting DDT's.
Even though it's called white hot spikes, and the artwork shows spikes that are white at the top and orange at the bottom, the spikes actually appear reddish-orange in the middle with black at the bottom, although the very tips are white.
Despite this, the artwork looks very white.
MOAB-SHREDR Spikes have the picture of white hot spikes on a MOAB even though this upgrade can be reached without buying the white hot spikes upgrade (e.g. 1/3 spike factory).
The bottom of the spikes aren't hot, because they are black and not red or white.