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koyunbaba
09-16-2018, 01:19 PM
Hello: I found this old on-topic thread, but I thought it might be OK to post a new thread, as it might evolve into repairs.

http://forum.woodenboat.com/showthread.php?8971-Preparing-Sitka-Spruce-Mast

I'm refinishing my Sitka Spruce masts. They are outdoors, but under cover (dry when it rains). I've stripped off all the old finish, and I'm anxious to get a few sealer coats of varnish on to stabilize the wood. I'd like to address the stains, and the following photos show some examples.

22962

22963

22964

Based on advice from the old thread, I plan to scrub with diluted oxalic then rinse with water. Two questions, though:

(1) How much dilution? 50/50?

(2) How long to wait until rinsing?

Thanks in advance, and I'll keep everyone posted on the progress.

pcford
09-16-2018, 02:57 PM
Sand down to 120. I always prepare the solution as strong a possible. Put in acid crystals until the solution will no longer absorb. Paint on the solution. Repeat as necessary. Neutralize with vinegar. Sand with 120 using a VERY GOOD respirator. Sand down the rest of way. Varnish.

Jay Greer
09-16-2018, 09:53 PM
I use hot water to dissolve oxalic acid. When it will take no more crystals I apply the hot acid to the wood. I also neutralize the acid, once the bleaching is done by applying a solution of Arm & Hammer baking soda powder and hot water to the wood surface. soda is a base and a base is needed to kill the acid. Other wise, the varnish will remain tacky and will not dry for a long time! Incidentally, that spruce looks a lot like fir.
Jay

pcford
09-16-2018, 10:17 PM
Yes, Jay is correct, the oxalic acid crystals should be dissolved in hot water.
Neutralizing the oxalic acid with a base like baking soda makes sense. However, it will make a horrible mess. Vinegar is an acid of course; it does not make sense to "neutralize" acid with an acid. However, that is exactly what Daly's recommends on their bottles of oxalic acid.
I stress again the importance of a very good respirator. Neglect at your risk.


I use hot water to dissolve oxalic acid. When it will take no more crystals I apply the hot acid to the wood. I also neutralize the acid, once the bleaching is done by applying a solution of Arm & Hammer baking soda powder and hot water to the wood surface. soda is a base and a base is needed to kill the acid. Other wise, the varnish will remain tacky and will not dry for a long time! Incidentally, that spruce looks a lot like fir.
Jay

koyunbaba
09-16-2018, 10:35 PM
This is all excellent advice, so thanks. I have three types of respirator: half mask with filters, full mask with filters, and a full mask supplied-air respirator. Thanks for stressing the importance of the respirator, too.

Regarding the neutralization, http://www.highlandwoodworking.com/woodworking-tips-1111nov/alannoel.html recommends baking soda.

koyunbaba
09-16-2018, 10:41 PM
Incidentally, that spruce looks a lot like fir.
Jay

Supposedly the masts were made from sitka spruce, but it's certainly possible that the builders used fir. It's a Cheoy Lee Offshore 40, 1970. Here's look from a few months ago as I was finishing up the new cap rail:

23025

pcford
09-16-2018, 11:28 PM
This is all excellent advice, so thanks. I have three types of respirator: half mask with filters, full mask with filters, and a full mask supplied-air respirator. Thanks for stressing the importance of the respirator, too.

Regarding the neutralization, http://www.highlandwoodworking.com/woodworking-tips-1111nov/alannoel.html recommends baking soda.

I know it makes sense to use a base, but I have done it and it made a horrible mess. Foaming up and discoloring the wood. And as I said the instructions on the jar of oxalic acid says to use vinegar. Never had any problem with varnish sticking.

pcford
09-16-2018, 11:30 PM
This is all excellent advice, so thanks. I have three types of respirator: half mask with filters, full mask with filters, and a full mask supplied-air respirator. Thanks for stressing the importance of the respirator, too.

Regarding the neutralization, http://www.highlandwoodworking.com/woodworking-tips-1111nov/alannoel.html recommends baking soda.

You might use the supplied air mask. That stuff is horrible.

Jay Greer
09-17-2018, 01:52 PM
Another thing, to neutralize the oxalic acid, that can be done is to first wash the wood with water followed by ammonia in solution. If that is too much work then just wash the wood. Yes, if the acid is not nuetralized, the first coat of varnish will remain tacky and attract all manner of air born crud. A second coat of varnish over it will dry but there will always be a chance of the varnish blistering at a later date.
If you don't have a respirator, try to stand on the upwind side when sanding. I prefer the respirator over going into a coughing jag as the acid dust can be very irritating!
Jay

skaraborgcraft
09-17-2018, 02:37 PM
I have only ever used water when washing off oxalic, and never had any issues when overcoating.....just saying. Gloves on the hands and googles are a good idea too.

Bob Cleek
09-17-2018, 02:38 PM
Truth be told, Sitka spruce doesn't bleach worth a damn. Some species bleach beautifully, such as teak. I've poured gallons of oxalic acid over Sitka spruce spars trying to get the grey discoloration out of them, generally to no avail. Your mileage may vary. Good luck! While a fair bit is removed by the acid, it takes sanding the discoloration off to really get rid of it.

Given Sitka spruce's limited decay resistance and the tendency of varnish to let go and peel off of softwood if moisture gets into the wood beneath the varnish, I'd recommend a very good soaking with CPES as a sealer beneath the varnish with particular attention paid to fastener holds. Others may have different opinions, but my experience has been very good with this application.

Jay Greer
09-17-2018, 04:15 PM
If spars are to be varnished, consider not using clear penetrating epoxy as a sealer and dunking the tip of each fastening screw in melted bee's wax before they are driven.
This will seal the wood against moisture intrusion and no staining around fastenings will occur. If you do seal with epoxy, there is always the chance of water getting in under the finish and staining the wood irreparably! Once the moisture gets under the epoxy there is no way to cure the problem of staining!
Jay

koyunbaba
09-20-2018, 01:28 PM
Yeah, I'm going to stick with one-part vanish for all brightwork. Too much work getting it back down to bare wood.

Anyway, two more questions:

(1) How long to let the oxalic solution sit before rinsing and neutralizing?

(2) Same treatment works well for cleaning teak?

Jay Greer
09-20-2018, 02:39 PM
Oxalic acid can remain on the wood and be re-dampend with a fine mist of water and allow it to bleach more if the stains are not gone. This should be followed by rinsing with fresh water and neutralizing with a base such as ammonia or a soda water solution.
It will work for teak that is to be varnished but, it is too strong to be used on a regular basis on teak that is to be left raw.
For teak decks the traditional bleach is citric acid which is available in powder form from chemical supply houses. It will turn teak decks silver white. Wash down decks, sprinkle on citric, scrub with fine brush cross grain and rinse. Voila pristine decks just as in the Royal Navy!
Jay

koyunbaba
10-10-2018, 08:17 AM
I did the oxalic acid treatment, with little to no improvement, and I've washed the masts in both vinegar and baking soda (twice). In any case, my rounds of sanding are helping and I've moved on to repairs, so please feel free to chime in again. You guys are great. Here are some pictures of a few trouble spots.

(1) An open seam, partially along a joint contains some rot. The width of the opened up area is about 1-2 cm. I'm thinking I'll have to scarf in some new wood here.

24315

(2) The mainsail track was held on with mostly screws, but also a drift bolt every 2 meters or so. I had to remove the bolts to get the track off and in it required making circular holes about 3 cm in diameter, but not all the way through the wood. I'm thinking clean up and plug these.

24316

(3) Mystery hole. Are there critters that would do this, or is it more likely that my mast was set down on an upturned bolt? (That's about 5 mm in diameter.)


24318

David G
10-10-2018, 08:34 AM
Not enough fotos to be sure, but that looks to me to be the site of attachment of some previous something (hardware?). Nothing in the images to hint at size. Small can be filled with a variety of things. Large can be remedied by a patch ('dutchman').

guillemot
10-10-2018, 09:03 AM
Buprestid beetles frequently leave "D" shaped exit holes like that, but that would have happened when the tree was alive.

Jay Greer
10-14-2018, 03:36 PM
Notice that the holes in the above foto are almost a pattern. Perhaps they held a tang plate at one time.
Jay

koyunbaba
10-24-2018, 11:55 AM
Notice that the holes in the above foto are almost a pattern. Perhaps they held a tang plate at one time.
Jay

Correct.

Anyway, I've gone ahead and patched up that rot. Here are some pics:

My initial thinking was to set up a jig for the router.


25063

I abandoned that track early on. Getting the orientation of the rails right as I moved the jig from place to place would have been difficult, and a local shipwright suggested doing the repair by hand. I'm sure the following photos are self-explanatory for most of you.

25064

25065

25066

25067

koyunbaba
10-24-2018, 11:58 AM
I sanded all mating surfaces with 60-grit, cleaned with acetone, then applied first unthickened, then thickened epoxy.

25068

25069

I used the power planer, then orbital sander to finish the job.

25071

25072

Jay Greer
10-24-2018, 12:20 PM
You have done a nice job on the repair! Hats off, Huzzah!
Jay

koyunbaba
10-24-2018, 12:53 PM
Thank you, Jay. Means a lot to me (both your compliment and having been successful at the repair).

In the end, this was not the most difficult or complicated project I've done, but it was the most intimidating!