Oil based v. Water Based

[John Branam]

Is there an advantage to using oil based finishes (this is the only type of finish I have used) over water based? Can you put water based finish over shellac?

[jeremy levine]

Is there an advantage to using oil based finishes (this is the only type of finish I have used) over water based? Can you put water based finish over shellac?

Please search the site this is a huge topic. Also check this site for a ton of info
http://www.targetcoatings.com/

[Jim Becker]

Oil-based finishes and water borne (not "based") finishes both have good points.

The former can sometimes enhance the figure of the wood and there are any number of variations in formulas to meet the most esoteric finishing requirements. Folks like the "warm" look they provide, too. For varnish, the most common oil-based products used in woodworking, there are three basic resin types used as a base: alkyd, phenolic and polyurethane. Most use BLO as the oil base, but some use some quantity of tung oil instead and there are now some formulas that use soya oil for a "lighter" coloration. On the downside, they dry/cure slowly, generally contain substantial quantities of VOC (volatile organic compounds), have fire dangers inherent and are "less convenient" to clean up. With laws governing such things changing and getting more strict, oil-based finishes will likely become less common over time, particularly in gallon cans. Application is generally brushed, wiped on or sprayed...the latter is less desirable in many cases since these products dry very slowly, relatively speaking, and re-coating times are wide.

Water borne finishes--water borne because the actual finish is suspended in the water, not "thinned" by it--are becoming more and more popular. Nearly all, if not all, are acrylic based products and there is a growing number of formulations on the market that are designed to provide a variety of characteristics during application and during the wear life of the project to which they are applied. Water borne finishes typically dry quickly and have limited VOC. For this reason, they are being embraced by more and more people and firms for the added safety; both in health and in low or no explosion/fire danger. On the downside, they are not as "warm" as oil-based finishes, although that is something changing quickly as manufacturers work on the formulations. Spraying is often the best method for application, but there are also brush-friendly formulas available. Wipe-on doesn't work well with water borne as it dries very quickly.

Personally, I almost never use oil-based finishes on furniture, although I do use them on turnings. I generally spray water borne with great results. To get around the "warmth" situation, I start with an application of BLO followed by a seal coat of de-waxed shellac in a "color" appropriate for the project. (You must use de-waxed shellac under a water borne finish or anything containing polyurethane) The combination of oil and shellac enhances the wood and its color before the water borne product is applied. In some cases, adding a slight amber dye to the water borne product can also be used to make it closer to oil-based varnish in appearance...some manufacturers are actually tiniting at the factory in that regard.

[John Branam]

Great info Jim. I have used several manufacturers oils based stains, as well as wipe on poly. I have used General's oil poly blend on my last few projects. I have a basement shop and I really want to cut down the fumes and related odor inherent with oil based products. I currently do not have the equipment to spray any finishes, have you brushed water borne finishes? What are the advantages or pitfalls of brushing them?

[Howard Acheson]

To add to Jim's excellent response you asked: ""Can you put water based finish over shellac?""

Yes you can as long as the shellac is dewaxed. Waterborne finishes do not adhere well to shellac that contains its natural wax.

[Cliff Rohrabacher]

I think the water urethanes are fussier.

They respond negatively to a more things than oils.

Example: if your sand paper has sterates in it you will likely have trouble getting a good finish with the water urethanes. Oil is way more forgiving.

[Chris Padilla]

Sterates can be taken care of with a good wiping of a pre-conditioner. Sometimes basic soap and water can work, too, but these typically shouldn't be used on bare wood for obvious reasons (grain raising).

One warning about water-bourne products and I don't care what the label says: they will raise the grain and will require sanding after application. Well, at least I have yet to find a water-bourne product that doesn't raise the grain (CyrstaLac, Fuhr, Target).

A first application of dewaxed shellac is a good way around the grain raising....