Can chipboard shelves be varnished?
By Googling for "chipboard sealant" I found a UK vendor of "work top edge sealer" that seems to be designed for that sort of job.


  
  Seals &amp; Waterproofs Sawn Or Drilled Edges, Joints, Sink Cut Outs etc.
  Excellent sealing and waterproofing properties.
  Ideal for use on MDF, Chipboard, Timber etc.
  Prevents water ingress into sawn edges.
  Easy to use and fast drying.