<p>I want to print a structure that I can embed in a resin and later dissolve. I know that some fancy 3D printing systems have raft materials etc., that can be printed and later removed easily. </p>

<p>Can any one suggest a 3D printing material that can be dissolved in say water or another readily available solvent?</p>

ABS dissolves in acetone. Indeed actone can be used to clean up 3D prints, see
What's smoother? Acetone treated PLA or ABS
. PLA maybe not somuch as ABS, see the same post.
PLA dissolves in any chlorinated or fluorinated solvent, such as THF or Chloroform - both of which are significantly more hazardous than acetone.
Hence, as always
take care
when using solvents, see
Safety precautions when using acetone
Also, as filaments are often not pure ABS or PLA, due to additives and dyes, etc., then the solvent may not dissolve the 3D printed part
completely
, and you may be left with a deformed, rubbery residue.