Olive wood from California orchards is prone towards developing cracks and checks very easily. It is a beautiful wood and it is stable once it has dried.
Here is what has worked for me in dealing with olive wood for turning. I recommend that you have some Green Wood Sealer on hand.
I brush green wood sealer over the entire piece of olive wood, which means the ends (number 1 priority and it is best to double coat them) as well as the faces and sides. Keep the olive wood in a cool dark place for long term storage, away from the sun and the wind.
I like to twice turn bowl, vessel blanks or any object that I turn from green wood. Here is the procedure I follow:
1) The first rough turning is to shape the object and get it down to a wall thickness somewhere between 1 inch to 1 and a half inches thick. As soon as I have completed the rough turning, I completely submerge the bowl or object in denatured alcohol. I have found that using a heavy duty contractors 3 mil garbage bag works well for conserving the amount of alcohol needed. Place the object in the bag and fill it with denatured alcohol (available at all hardware and paint supply stores for thinning shellac etc.) until the object is completely submerged, then close and secure the bag with a rubber band or spring clamp. Allow it to set for 24 hours. The alcohol will displace the bound water inside the cell walls of the wood. Take it out and place it upside down on a rack and let it drip dry for another day with a paper bag over it to block air movement. Look for the start of any checks and if you see any then apply CA glue (cyanoacrylate) over them right away. The CA glue will adhere to wet wood and stop the checks from progressing.
2) To further prevent checks, I paint the object completely with green wood sealer again.
This will slow down the drying process. Usually the alcohol treatment will dry the rough turned object within 2 weeks which is great, and then you can remount the piece and do the final turning and sanding and finishing. Since olive wood likes to check and crack easily, I have found it is worth the extra effort to paint it with green wood sealer (after the alcohol treatment) so that it slows the drying process and helps to minimize any cracks. This can slow the alcohol drying process down to 1 or two months but it is worth it to prevent those darn cracks.
3) Once the wood is dry (I use a moisture meter to check it and look for a 10 percent moisture content) then you can remount it on the lathe and do the final turning, sanding and finishing.
Another method to measure dryness is to weigh and date the rough turning and mark it on the wood. Keep weighing it and once it stops losing weight it should be dry.
If cracks have occurred, then I sand some of the olive wood with 220 grit sandpaper, take the dust and mix it with slow setting epoxy, and use it to fill the cracks. I also like to use black dye (mixol) and mix it with slow setting epoxy to fill any bark inclusions, knots or other areas where it seems appropriate.
Fine work requires extra effort. Put in the work and your pieces will reflect that effort.
I wish you all the best in your wood turning,