There are many exotic wood species that are extremely beautiful, but due to some of their special characteristics, they can present their own challenges. Most often there are concerns about woods that are naturally very oily, dense, resinous or high in tannins.
Naturally Oily Woods
Many exotic woods contain a high amount of natural oil that can sometimes make them difficult to finish. Some common oily wood species would be Ipe, Teak, Purpleheart, Bubinga, Santos Mahogany or any species of Rosewood. These oils tend to make it difficult for some coatings to cure properly or even coat well in the first place. You may need to do some preparation to minimize the effect of the oil or seal it in. Always test your process and full finishing system to ensure proper adhesion.
Preparation
Regardless of the finish being applied, it is a good idea to wipe down oily woods with some solvents to remove as much surface oil as possible to allow for good penetration and adhesion. After prep sanding to your desired level, wipe the surface down with denatured alcohol, acetone or lacquer thinner to “dry” out the surface. Let this dry for at least 15-20 minutes before applying any Waterlox products.
Waterlox Sealers
Waterlox sealers (UNIVERSAL Tung Oil Sealer, ORIGINAL Sealer & Semi-Gloss Finish, and MARINE Sealer) can all work well on most oily woods without additional steps. Prep the wood as mentioned in the previous step and then continue as normal. The tung oil tends to blend well with the natural oils and can create a well cured surface. Allow more than 24 hours on the first coat if possible to ensure as much oxygen can reach the bottom seal coat.
The only exception to this rule would be Cocobolo. For Cocobolo or if you’d like additional insurance, it is best to “seal in” the oils before coating.
Sealing in the Oils
Use a thin cut (1-2#) of dewaxed shellac to both further dry out the wood (because its alcohol-based), as well as plug up some of the pores. Once dry, lightly sand with 320 grit paper, 0000 steel wool or a maroon scotch brite pad and continue coating as normal.
Very Hard/Dense Woods
Many exotic woods are also extremely dense. This can make it difficult to get good penetration and adhesion on the wood. Some common woods that fall under this heading would be Ipe, Cumaru and Ironwoods. These woods usually feel extremely heavy compared to other woods that are cut to the same size.
Waterlox Products on Dense Woods
There are typically no concerns with using Waterlox products on very dense woods. All sealer products will work well and tend to act as good primers for the subsequent finish coats. There are a few points to pay attention to however:
- Most dense exotics are also relatively oily. Follow the Preparation step from the previous section and at least wipe down the surface.
- Rub-in and buff-in products will not penetrate as well. Extremely dense woods are going to be much less absorbent, so you will probably use a lot less product.
- Stop sanding at a lower (coarser) grit. Sanding your surface to 100 grit instead of 220 will keep the wood surface more open and help penetration into a more dense wood. It is still important to sand well and not leave sanding marks, just stop at a lower number.
Resinous Woods
Some woods (or even some parts of the tree) may be very resinous. Some typical woods in this category would be softer woods from conifers such as pine, fir, etc. Typically, the heart wood will have more resin, so the most common instance will be on heart pine. These resins usually will dry/cure on their own and do not create much of a problem for Waterlox products. Again, make sure your surface is very clean and wipe down your project to remove any surface oils or uncured material. Wipe with paint thinner, turpentine or mineral spirits prior to coating. Typically the resins will play very little role in the application of the finish, but they will be much less absorbent over resin when compared to the very soft wood around them. This may make the initial coats look uneven.
High Tannin Woods
Many woods contain tannins which can cause problems for some finishes. Most likely, you’ve heard of tannins in wine as they are pulled into the wine from the oak barrels that they are aged in. Common high tannin woods are oak, cedar, walnut and some mahoganies. Tannins are water soluble, so when water-based finishes are applied they are essentially “activated” and converted to tannic acid. This tannic acid can cause staining (usually referred to as tannin bleed), discoloration or improper drying.
Tannins and Waterlox
Most Waterlox products are strictly oil-based and therefore will not interact with any wood tannins. The ORIGINAL Sealer, UNIVERSAL Tung Oil Sealer, and MARINE Sealer are all excellent sealers, as they will not interact with any of the chemicals in the wood and will allow for any finish to be applied over top, including water-based finishes. Because of the tannin content of certain woods, a sealer is required to use our H2OLOX finishes to prevent discoloration or drying issues.
