A mixture of at least two compounds each having at least two double bonds, said mixture having a WFR from 200 to 600 g/mol of double bond and at least two of said compounds each comprising at least two (meth)acrylic esters as double bond component, WFR being given by: ∑ i = 1 n ⁢ α i ⨯ MW i / Z i = WFR ⁢ ⁢ where ⁢ ∑ i = 1 n ⁢ α i = 1 αi is equal to the molar fraction of compound (i) in said mixture,n is equal to the number of compounds in said mixture and n is ≧2,Zi is equal to the number of double bonds in said compound (i),MWi is equal to the molecular weight of said compound (i).