Ice melts with a normale torch and it melts with glowstone but it doesn't melt with a restone torch.
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Ice melts if it has a light level of 12 or higher (http://minecraft.gamepedia.com/Ice). Redstone torches provide a light level of 7 (http://minecraft.gamepedia.com/Redstone_Torch). Therefore, redstone torches can't melt ice and this works as intended.
Ice melts if it has a light level of 12 or higher (http://minecraft.gamepedia.com/Ice). Redstone torches provide a light level of 7 (http://minecraft.gamepedia.com/Redstone_Torch). Therefore, redstone torches can't melt ice and this works as intended.