A substantially solid, solvent free, radiation curable composition comprising a) optionally from 0.1 % to 99.9% by weight of a colorant; and b) from 0.1% to 99.9% by weight of radiation curable polymer obtained from at least one mono-(terminal functional forming) monomer of formula I: R 1 (R 2)C=CR 3 (C=O)(X 1) n R 4 Formula 1, where n is 0 or 1, X 1 is oxy or -NR 5 - (where R 5 represents H or optionally substituted organo), R 1 independently represents optionally substituted C 1-10 hydrocarbo, hydroxyl, optionally substituted C 2-10 hydrocarbo-oxy comprising a ring moiety, and/or carboxy; and R 2, R 3 and R 4 each independently represent H, an optional substituent and/or optionally substituted organo groups and where n is 0, R 3 may also represent oxy or -NR 5 -; and c) from 0.1% to 90% by weight of a radiation curable reactive diluent with weight average molecular weight (Mw) of at least 100 daltons; and d) optionally from 0.01 to 10% by weight of at least one photo-initiator; and where the radiation curable polymer (b) is i) obtained by catalytical chain transfer polymerisation in a suspension polymerisation process using a cobalt catalyst as a chain transfer agent; ii) is solid under standard conditions; and iii) is mono-(terminal functional) comprising one terminally located activated unsaturated moiety (such as of Formula 1 herein). where the composition has at least one of the properties to: A) is substantially free of volatile organic compounds (VOCs); B) has a residual concentration of initiator (such as peroxide) of less than 0.025 g per g of polymer; C) comprises a polymer having a total ethylenic unsaturation (for example from moiet(ies) of Formula 1, such as C=C and/or (meth)acrylate) greater than 0.1 milli-equivalents C=C per g polymer; D) is substantially-free of sulphur comprising species; E) is substantially free of cobalt species; and/or F) has a weight average molecular weight (M w) of less then 25kDa. a) optionally from 0.1 % to 99.9% by weight of a colorant; and b) from 0.1% to 99.9% by weight of radiation curable polymer obtained from at least one mono-(terminal functional forming) monomer of formula I: R 1 (R 2)C=CR 3 (C=O)(X 1) n R 4 Formula 1, where n is 0 or 1, X 1 is oxy or -NR 5 - (where R 5 represents H or optionally substituted organo), R 1 independently represents optionally substituted C 1-10 hydrocarbo, hydroxyl, optionally substituted C 2-10 hydrocarbo-oxy comprising a ring moiety, and/or carboxy; and R 2, R 3 and R 4 each independently represent H, an optional substituent and/or optionally substituted organo groups and where n is 0, R 3 may also represent oxy or -NR 5 -; and n is 0 or 1, X 1 is oxy or -NR 5 - (where R 5 represents H or optionally substituted organo), R 1 independently represents optionally substituted C 1-10 hydrocarbo, hydroxyl, optionally substituted C 2-10 hydrocarbo-oxy comprising a ring moiety, and/or carboxy; and R 2, R 3 and R 4 each independently represent H, an optional substituent and/or optionally substituted organo groups and where n is 0, R 3 may also represent oxy or -NR 5 -; and c) from 0.1% to 90% by weight of a radiation curable reactive diluent with weight average molecular weight (Mw) of at least 100 daltons; and d) optionally from 0.01 to 10% by weight of at least one photo-initiator; and where the radiation curable polymer (b) is i) obtained by catalytical chain transfer polymerisation in a suspension polymerisation process using a cobalt catalyst as a chain transfer agent; ii) is solid under standard conditions; and iii) is mono-(terminal functional) comprising one terminally located activated unsaturated moiety (such as of Formula 1 herein). where the composition has at least one of the properties to: A) is substantially free of volatile organic compounds (VOCs); B) has a residual concentration of initiator (such as peroxide) of less than 0.025 g per g of polymer; C) comprises a polymer having a total ethylenic unsaturation (for example from moiet(ies) of Formula 1, such as C=C and/or (meth)acrylate) greater than 0.1 milli-equivalents C=C per g polymer; D) is substantially-free of sulphur comprising species; E) is substantially free of cobalt species; and/or F) has a weight average molecular weight (M w) of less then 25kDa. i) obtained by catalytical chain transfer polymerisation in a suspension polymerisation process using a cobalt catalyst as a chain transfer agent; ii) is solid under standard conditions; and iii) is mono-(terminal functional) comprising one terminally located activated unsaturated moiety (such as of Formula 1 herein). A) is substantially free of volatile organic compounds (VOCs); B) has a residual concentration of initiator (such as peroxide) of less than 0.025 g per g of polymer; C) comprises a polymer having a total ethylenic unsaturation (for example from moiet(ies) of Formula 1, such as C=C and/or (meth)acrylate) greater than 0.1 milli-equivalents C=C per g polymer; D) is substantially-free of sulphur comprising species; E) is substantially free of cobalt species; and/or F) has a weight average molecular weight (M w) of less then 25kDa.