Present participle; Past participle - blackening - blackened Present - blacken - blacken - blackens - blacken - blacken - blacken Past - blackened - blackened - blackened - blackened - blackened - blackened Future - will blacken - will blacken - will blacken - will blacken - will blacken - will blacken Present conditional - would blacken - would blacken - would blacken - would blacken - would blacken - would blacken Present Perfect - have blackened - have blackened - has blackened - have blackened - have blackened - have blackened Past Perfect - had blackened - had blackened - had blackened - had blackened - had blackened - had blackened Future Perfect - will have blackened - will have blackened - will have blackened - will have blackened - will have blackened - will have blackened Past conditional - would have blackened - would have blackened - would have blackened - would have blackened - would have blackened - would have blackened Imperative - - - blacken - - - - - - - -