About 6 years ago I realized tht I was suffering some health problems form the use of turpentine and turpentine-based oil painting supplies. I have tried many turpentine replacement systems and found most lacking.
Without sounding too much like an infomercial I want to share a great resource with you, Eco-House. Eco-House makes a solvent system that works with the painting supplies I already use. I don't have to change my materials just the solvent. Eco-House offers their solvent in a variety of strengths. I use the strong solvent to disolve varnish crystals and wax and the extra mild to thin paints and clean brushes. I have used the products for these 6 years without a problem either with my health or with the paint surfaces.
For more information visit Eco-House at:
http://www.eco-house.com/art_supplies.html