Applying Spar Varnish to a Mahogany Interior – Boston Whaler 13 Restoration – Part 11

Spar Varnish on Mahogany Roll and Tip

I bought this Whaler without an interior so had to buy one. Luckily, there’s a great craftsman in Haverhill MA who fabricates them out of real African Mahogany. Bob Latorelle put together a Super Sport interior for me at a fantastic price. The wood came unfinished so applying spar varnish was the first order of things.

I have finished many wood projects, usually with Polyurethane but wanted to keep this restoration as original as possible. I opted to use traditional Spar Varnish. After doing some research, I decided to use TotalBoats Gleam 2.0 Spar varnish. Chiefly because you can apply several coats without sanding in between.

But just as important were the components, Tung oil is one of the key components and my experience with it in the past has led to great results. Additionally, it has UV protection built in to it, which for an outdoor piece of mahogany is important.

I also used their a varnish sealer to help seal up the grain before applying any varnish. Anyone that has used varnish will tell you that many coats are required to seal the wood. Completely sealing up the grain will give you that deep gloss that highlights the natural patina in the wood. Using a sealer first helps.

Helpful Tips for Applying Spar Varnish

Controlling the Dust from Sanding

When applying spar varnish, or any wood finish, sanding dust is your enemy! Unfortunately, because of the area I am working in, creating a dust free environment is impossible. That being the case, I had to take extra measures to minimize the dust when applying varnish.

Whenever I sanded, I carefully vacuumed every area of the wood as well as the surrounding areas and the surface it was resting on. I also carefully wiped the piece I was working on with mineral spirits to get any dust off.

After sanding, I would let everything settle for at least a day before applying any varnish. I also took extraordinary precautions before applying spar varnish. Before any of the varnishing sessions, I carefully wipe down the piece with mineral spirits again. Then I go over the entire piece with a tack cloth. The only time I didn’t do this was when I was laying up several coats within a day.

Prevent Drips and Sags

One of the worst things that can happen when finishing wood is a drip or a sag. Sags can be prevented by carefully applying thin coats. It is preferable to have many thin coats than a few thick ones.

Drips are even worse. If you’re not careful, drips can run down the side of the piece you are working on. These are difficult to remove and require a lot of detail work. I remove drips by going around the piece after applying spar varnish and wiping the areas that I don’t want to varnish at that point with a shop rag or towel.

Varnish Shrinks when Drying

When you are applying varnish, it goes on relatively heavy compared to when it dries. What this means is that you may finish varnishing a section and it appears to have a nice even gloss with no grain visible. When you come back a few hours later, all of the grain is showing through. This is quite normal. You fix this by applying as many coats as necessary to get a smooth mirror like finish.

Keep the Varnish Clean

Make sure you run your varnish through a strainer prior to using it. If you have leftove spar varnish , run it through a strainer before putting it back in the can. That way, if it has picked up any stray particles of sanding dust, you won’t contaminate the can of varnish.

Take Care of your Brush

A key to a great varnish finish is using a good quality natural bristle brush. Badger hair brushes are the preferred brush of many pros in the trade. Unfortunately they are expensive!

Clean your brushes well and store them after a through cleaning and conditioning with a coating of diesel or kerosene (spin all the excess off). I typically clean my brushes with paint thinner or mineral spirits and store them in the original box wrapper they came in or make one with newspaper.

The one exception is when I am doing multiple coats within a day. I will store them in a container of mineral spirits or thinner, making sure they are upright in the container. When ready for the next coat, I will spin the excess off.

This also helps preserve the brush when you are tipping or painting with it. The thinner close to the heel of the brush will keep paint or varnish from loading up on the heel and make it easier to clean when you are through.

One last work on brush care. Never lay the brush down when you are not using it. It’s better to stand it upright in a paint cup or against a support. This is so that paint or varnish does not creep up into the heel. The die hard pros will drill holes right above the ferrule of the brush and attach a hanger so they can hang it in the side of a paint pot.

Good Bright Lighting is your Friend

When you are applying varnish, try to get as much lighting on the piece you are working on as possible. This is to help you detect any areas that you may have missed. Typically, they are not obvious at a glance. You will need to look at the work piece from various angles to see any areas that have been missed.

You are really relying on the glare from the lights to see this. The reflective gloss will be dull and drab in missed areas. It seems that at times, no matter how much you roll or brush over an area, there will be bare spots! Check your work frequently!

Sealing the Mahogany with Totalboat Varnish Sealer

When working with the sealer, I applied it to both sides using painters pyramids. These are handy since you can apply a coat on one side, flip it over to rest on the pyramids and put a coat on the other side. One word of warning however. The tips of the painters pyramids are hard. If you move the wood along the tip, or put too much weight on the wood, it will leave a dent or worse, a scratch.

Using the pyramids, I applied three coats of Totalboat Varnish Primer / Sealer with a foam brush within a 24 hour period, waiting until the last coat was dry to the touch before overcoating, no sanding between coats. When applying more than 1 coat, you need to let it dry for at least 48 hours before doing anything else.

Don’t forget to wipe the edges or sides where you don’t want any varnish drips.

Sanding the Sealer

After 48 hours, I sanded with 320 grit sandpaper using a Rigid Random Orbital Sander. But first, I took the mahogany off of the painters pyramids. I didn’t want to risk scratching or denting the wood, especially since there would be a lot of movement and pressure put on the wood while sanding. My key objective at this stage is twofold. First, level it out so there are no lumps or specks. I want to have a perfectly smooth surface for the Spar Varnish to adhere too. Second, leave a rough surface for the next coat to stick too.

First Three Coats of Spar Varnish

After all the sanding of the sealer was complete, I started applying spar varnish, I used three coats of Totalboat Gleam 2.0 by rolling and tipping within a 24 hour period, no sanding in between and applied varnish when last coat was dry to the touch.

Rolling the Spar Varnish

When rolling the spar varnish on, make sure that you use a high density fine finish foam roller. You want to load the roller with enough varnish to do a small section at a time. In the case of this bench seat I was rolling a section about 16″ x 12″ at a time. A critical aspect of using the roller is to spread the varnish evenly.

Tipping the Varnish

Once you have rolled the varnish on, use a good quality natural bristle brush. I used a 2.5″ Redtree badger hair brush. That particular brush has turned into one of my favorites when tipping off varnish or topside paints. You want to hold the brush at approximately a 45 degree angle to the surface. Brush from the wet edge you just layed on into the last area you painted and always brush with the grain.

Remember to always tip from the freshly applied wet edge to the last section painted, overlapping the two sections. Also remember that tipping off is to level a surface and is not used to apply paint or varnish.

Sanding the first Three Coats of Spar Varnish

For this stage, I waited 48 hours and then sanded the varnish down with 320 grit paper with a random orbital sander. Once again, my objective was to get rid of any speckles and bumps and leave a perfectly smooth surface. If you have any drips or bumps in the varnish, this would be a good time to sand those down.

Applying the Next Two Coats of Spar Varnish

For this phase, I basically repeated what I had done when applying the first three coats. After a thorough cleaning, I applied the first coat by rolling and tipping. After the coat had dried to the touch, I applied a second coat of varnish using the same technique. Both of these coats were applied within a 24 hour period so no sanding between coats was required.

Applying Spar Varnish Finish Coats

Wait 48 hours before doing anything else. This gives the last two coats of Spar varnish adequate time to dry so that it can be sanded. At this stage, you should be ready to apply finish coats.

Applying the first Finish Coat

First, sand the last two coats of varnish with 320 grit sandpaper. At this stage, I preferred to sand by hand rather than use a power sander. Sanding by hand gives me a bit more control over how much to remove over a given area.

Once you have sanded the work piece down, vacuum up the sanding dust. I prefer to let everything sit for 24 hours to let dust settle but you can go right into it if you prefer. Wipe everything down with mineral spirits. After the piece dries, give it a once over with a tack cloth before varnishing. Next begin applying Spar Varnish by Rolling and Tipping it on.

Final Finish Coats

To get the final finish coats on, you basically repeat the steps for the first finish coat. Sand, clean then roll and tip a coat on. The number of coats of Spar Varnish you apply is entirely up to you. Totalboat recommends a minimum of six. I would suggest that you apply enough coats so that no wood grain is visible in the glossy surface.

 The more coats you apply, the more depth and and gloss you will get. This particular piece I am working on took eight coats. I had to stop myself there or I would have kept adding coats. 

Check out the YouTube version of this article That was featured on TotalBoat’s blog here: Varnishing a Boston Whaler Mahogany Interior – Boston Whaler 13 Restoration Part 11

Make sure to see the entire series of articles on this Boston Whaler Restoration Here: Boston Whaler 13 Restoration

Previous Whaler Restoration Article

Next Whaler Restoration Article

Coming Soon

Below are affiliate links to some of the items I used in this article:

%d bloggers like this: