My goal with this piece was to retain the shape but not necessarily the texture of the outer edge.
The first order of business was to fill the split that had developed while the wood was drying. To do this I created a dam out of waste wood. Before securing it to the pine I coated the dam with 5 layers of mold wax. This would allow the dam to come away when the epoxy hardened. The dam was held in place and thoroughly sealed using a hot glue gun.
In order to keep the epoxy bubble free on the one hand and from cracking on the other, the gap was filled in a series of pours. While this takes longer, patience is rewarded by having a minimum of frustration.
A thorough wash coat of epoxy was applied to the piece to give it integrity. A thicker coat of epoxy was then applied to fill in the myriad gaps around the edges.
Once out of the makeshift mold, the bottom was given a similar treatment to fully seal the wood.
Once on the lathe, the pieces was turned in several sessions with wash coats of epoxy between each one.
Again, this is a time consuming procedure but it prevents irreparable tear out. The wash coat of epoxy needs at least 24 hours to harden sufficiently. I usually allow longer if there is no rush for the piece; sometimes several days.
This cross section was turned as a shallow bowl.
Completing the edge required additional patience. I waited until the front and the back were turned and sanded before addressing the edge. This meant that there was no excess surface area to smooth out.
Please remember that you can click on any image to see an enlargement.
There is more to come.
Due to the irregular shape of the wood a regular mold was out of the question. However, some kind of containment was necessary as the perimeter of the wood was porous and soft.
To accomplish this I placed the wood on a new, clear garbage bag (epoxy doesn't stick to a plastic garbage bag) and wrapped the outside with masking tape and then sealed that with packing tape.
Below is a view from the top and to the left is a detail shot.
I put the lathe on the slowest speed and allowed the sander to follow the edge. It took some time but I was able to sand through the grits to 1000. Normally, I don't sand to such a high grit when working with pine but the epoxy requires this to eliminate the scratches.
Although challenging, this slab turned out quite well.
I called the piece "Life Span". It was about 16 1/2" in diameter by 1 5/8" tall.
I have talked a lot about epoxy in the previous posts without giving much information about it. I hope to rectify that here.
Where I get my epoxy and what I buy
First of all, I buy most of my epoxy from Noah's Marine. Info on Noah's can be found here (scroll down). Specific info on the resin can be found here. I use the medium hardener. I also use the pigments that Noah's provide. They can provide measuring accessories as accuracy is essential.
There are many epoxies
I have tried other epoxies but for the most part they have specific uses and are not applicable to my situations. Some are meant to cover artworks with thin clear coatings. Some are more UV stable than others. Some require higher room temperatures to work or set properly and thus need to be set in warm water baths.
(An update here. I had a problem with some of Noah's epoxies and that problem is detailed here. If the page asks for a password, please use 'noahs'. This is part of the experimenting that I did. The resulting piece was not very successful.)
I use wash coats to penetrate rotten or very soft woods to give them integrity for turning. On end grain a wash coat will go in up to 5/16" (8 mm). In soft wood such as spalted the depth can be anything from 1/8" to 3/16" (3 mm to 5 mm)
When I mix my epoxy it is 2 parts resin to 1 part hardener. To make a wash coat with the viscosity of water I add another 1 part of lacquer thinner. If a thicker coat more like a thin syrup is desired then I use less lacquer thinner. Stir the epoxy resin and hardener first then add the lacquer thinner.
Two cautions about the lacquer thinner
A mask is definitely needed when working with the stuff. It smells bad and can give headaches. I get migraines from it. When I am using it I make sure that the application is the last thing I do before I leave the studio for the day. My studio is in a separate building. This should not be done in a home workshop that is part of the house.
Secondly, the hardening of the epoxy takes considerably longer when using lacquer thinner. It can take from several days to more than a week. Lacquer thinner also weakens the epoxy. I don't use this technique for anything else.
Turning wood strengthened with a wash coat
When I am turning end grain such as that described in the previous posts, I only turn the epoxied wood until the wood starts to tear instead of cut. I find that using a very sharp gouge, the transition from the epoxied wood is readily apparent. At this point I stop and apply another wash coat. It takes much longer to turn a piece this way but the integrity of the wood is essential to the success of the piece.
Sanding and finishing after turning
After I have finished with the gouge and am ready to sand, I apply one last wash coat. This makes the turned surface hard enough to sand and will give the entire area to be sanded the same density. This is important as I do not want to introduce texture where none is desired.
I usually sand from Grit 60 to 1000. Going all the way to 1000 is not necessary unless there are large areas of clear epoxy to be sanded. The reason for going to 1000 is to completely removed the sanding lines. I am able to apply my finish over the epoxy but I try not to use more than 3 coats.
I hope this covers some of the questions that may have arisen in the previous posts. I will go into sanding and finishing in more detail in a future post.
Remember that you can click on any image in my recent posts to see an enlargement.
A quick addenda to my last entry.
As I have said, I leave my finish tins upside down on an angle so that finish only accumulates in the reservoir. When I am ready to use the finish, I flip the can over but leave it on the angle. This allows the finish to drain down from the sides and lid of the tin. If I flip the can over as the first part of preparing my finishing materials, this gives plenty of time for the liquid to drain down.