Help! Wood least likely to crack?

[tree-ni]

Hello everyone. I work for a social enterprise that trains school leavers and the long-term unemployed in woodworking skills, mainly site and bench joinery. Building on one of our key workers talents we've been developing chainsaw carving to support our training activities.

We've been at it for a number of years and are slowly gaining experience but one of the issues we are having is the cracking of carved wood over time. Normally I wouldn't be too concerned as its part of wood's feature but when doing commissions for schools I am concerned about children's fingers getting caught in cracks.

To date for our larger commissions we've used oak as it is hard wearing and was recommended to us, but I've seen this crack quite badly. Is there an other wood anyone can recommend?

Also, can anyone give any advice on finishing? We started by just using decking oil on our smaller pieces but have been using danish oil on our large oak commissions. Is there anything else anyone could recommend for a nice, high quality finish? Is it common to finish with varnish, and if so what kind?

Thanks for reading this and thanks for you time.

[jefftaylor]

hi there tree-ni

im guessin your carving logs when you say chainsaw carving, and there all going to crack over time but i will let somone with more experience tell you abut it. i have been using a two part epoxy called envirolite tek on alot of carvings ( but it is expensive) but works great.The first coat soaks in alot but bindes the wood together. also it is very thick (self leveling) so you need to check your carving alot for dripping and blowtorch any bubbles out. its hard to work with but the finish is like glass! the carvings i have been using this on arnt cracking yeee haaa!! check it out

\jeff

[CarverFromNoWhere]

I think I would try some white or red pine, you wont be able to get the super details as with oak but the pine shouldn't crack as much.
Carl

[Rwenzoski]

Hi Tree-ni, I have been chainsaw carving for a few years & tried almost every finish on the market & have a lot of relative expeirience from log buliding, owning a body shop plus building a cedar stip canoe & kayak, I agree with Jeff about the epoxy but have a little different logic from my experiences. I use a product called "Rot Fix" or "S1". Both are very low viscocity resins (almsot as thin as alcohol) & form my experience if you use a higher viscocity of any finish more of it sits on the surface & doesnt peneterate as deeply to "stabalize" & not seal the wood. This is the function I look for as the deeper the penetration the more of the outer shell is stabalized & when I use these two products I keep applying until the wood will not sturate or absorb any more product. When it dries even on a lot of different types of green wood the finish is dry. The advnatage of this is the the ony time MOST epoxies are toxic is when you sand them, CPES is the exception to this rule & either a fesh air supply or an oxygen respirator should be used. If the types of epoxies used yeild a glossy layer on the outside this is a finishing type epoxy or the first coat has been allowed to flash off (first stage of drying) & then another coat applied which doesnt penetrate. All epoxies must be sanded before topcoating or there is very little chemical adhesion & almost no mechanical adhesion. With using these two products the sanding isnt necessary with the exception of the odd spot where the epoxy may pool. I normally wait until smal checks appear in the surface before applying this epoxy & then I use automotive grade polyurethane enamel as a top coat as epoxy has no UV inhibitors to resist our cuastic sun nowadays. The cost of these materials seem very high initially but in the long run it works out to about 30% more than stains, varathanes, varnish or anything else available. A person must also be careful of sealing carvings up too tight as this can result in the carving rotting form the inside out. Jeff, you say no cracking but this is a result of slowing down the dryuing process & this is what I try to achieve before applying any finishes then the mopisture content is lower & less chance of the carving rotting inside the sealed finish. As far as wood that cracks the least, it all cracks & the larger the cells & higher the moisture (water) content the more it will crack when exposed to the sunlight or heat. When I am doing a large, off the stump piece, what I have found works the best is as soon as you are finished carving (even for an hour) is t cover the carving with plastic, clear is fine if inside or a dark tarp if outside as you must keep it out of the sun. The seal of the plastic or tarp is determined byu the first couple of times you take the cover (what ever it is) off & see what amount of moisture is trapped under it. Normally I get at least condensation & I shake this off, turn it inside out & recover the carving. Most times it can hang loose or be tied just loosely around the base if in the wind but I have had some large cell types that must be actually wrapped tight to retain moisture as long as possible & the plasitc or tarp "wicks" the moisture out at a controlled rate & this is the secret of minimizing the cracking due to quick moisture loss. That's al I can think of or have time for the moment but will answer any questions & go carve & think about this for a bit!
Thanks, Robbin
A couple of other thoughts to add to minimize cracking.
a lot of carvers especially production carvers kerf thier carvings on the back side which should always be the side with the shortest distance to the sapwood from the heart, least path of resistance, right!
If you can get logs large enough to carve the entity you want out of a half log is best also & if carving thin, do it then get it covered or add the epoxy quickly & I have had a few with no cracks at all from doing this.

[highsierrabear]

Wood cracks. (period)

As a log dries the wood cells give up their moisture, shrink and collapse. This happens with most wood. The collapsing of wood cells causes stress in the wood, hence cracks.

Many of the elite chainsaw carvers basically state that their work is guaranteed to crack.

Some carvers used kiln dried boards laminated together. Very expensive and time consuming.

Some carvers use relief cuts to relieve stress in the wood and "pull" cracks into a benign side of the carving.

Also, keeping your carvings well "moisturized" with regular coats of high quality sealer will help.

Use what you've got to work with. Oak is hard, and probably dificult to learn with. Pines, firs, redwoods, and cedars are probably the easier woods to start with.

[tree-ni]

Thank you everyone for you advice. Its much appreciated. I'm having trouble finding a good sealer. Can anyone recommend some and tell me why they use it over, say, danish oil. Its not something I know a lot about and this would be a great chance for me to learn about different finishes.

[tcb16]

Hi Tree-ni

I'm not sure of the characteristics of the Danish Oil your using, but I can offer a few ideas. Look for something with UV protection, as paint and burning will both fade over time without it. The rotfix that Robbin talks of is really good stuff, and although it's priced on the high side it really does go on thin and last a while. I actually learned of it from a seminar Robbin taught at the Ridgway Rendezvous a couple years ago, and have been using it ever since.
Tim
PS - thanks for all of your contributions Robbin!

[Schaef]

Tree-ni,
Here's one way to MINIMIZE cracking in a large piece: make a long cut starting from the top going 3/4 of the way down thru the center of your log, then turn the cut to the outside of the log. Set the smaller piece aside. The remaining piece will provide a heavy base to support your work, and a "half-log" in which to carve. The half log has significantly less stress because the sapwood has a place to expand. (Think of this as a super-wide kerf cut). Watch as the base develops tiny cracks and work those cracks into your design - for instance, position the crack between boulders carved into the base. When the cracks grow, they will be inconspicuously disguised in your piece.
Schaef