Restoring an Etch

Bob Smalser has talked about this: https://www.woodworkforums.com/f127/n...oration-57366/
using a product called Oxpho-Blue

Here's another link regarding using "Brass Darkening Solution": Enhancing the Handsaw Etch by Bob Sturgeon
a search about suggests it contains selenious acid (Selenous acid - Wikipedia, the free encyclopedia)

BobL mentioned in the Citric Acid thread (I think) that the acid has a blueing effect ... which together with other tidbits I had come across lead me to try phosphoric acid on a test saw. Phosphoric is a rust-converter, and I have a 4L container of it because it is a 'gentle' acid for cleaning the element for salt-water pools. (When we first moved here we used diluted hydrochloric acid)

Naval jelly is/contains phosphoric acid.

Bob Smalser has also mentioned leaving a phosphoric acid solution on saws "overnight" ... but no details about the concentration. The solution I have is 40% by weight - which I expect is quite concentrated.

I tentatively tried it on a Spear & Jackson 888 that I am slowly rehabing ... I could see it bubbling slowly on the surface ... and only left it on for 5 mins.

Attachment 248194 Attachment 248195

On carefully sanding the etch was not visibly improved. The blued area I think is now lighter (I haven't taken 'after' photos yet) ... so the etch is probably a bit less visible than before :) Hmmmm.

So a few points.

I like this saw, so I won't experiment too heavily with it. It isn't an old old saw - so maybe the etching has a different character to it. I will try (part of) a beaten up early 1900s Disston #7 etch next and see how that goes.

I'm thinking about reducing the concentration to 10% and giving it more time to act.

I'm also in two minds about the sanding. There is a theory of using a sanding block so that the abrasive isn't pushed "down into the etch" and does more sanding on the rest of the steel. I have been happy up until now with using my three fingers together on the 'sandpaper' ... because you have a more direct connection with the pressure being applied to the steel. This has worked ok for me with cloth-backed paper (P120-P240) and thin P2000 from the auto shop.

I tried it half and half on the blued section, but had the same result either way.

That's all I have so far.

Cheers,
Paul.

What I forgot to say was that I have in the near-recent past tried to clean carefully over an etch, and felt that I had reduced its visibility. On having put this aside for a couple of months, I have found - on revisiting it - that it has regained its (limited) visibility as it seems to have 're-patinated' (if that is a word) to some extent.

I have photos of this saws etch that I took some time ago ... it will be interesting to see if it looks any different (to now) in a month or two.

Paul.

I wouldn't use fingers and paper when sanding the etch. Fingers are soft and will push the abrasive into the etch. Better with abrasive glued to a small board or block and sanding lightly over the etch and checking constantly. I fear have learnt this with experience. As for enhancing the etch I would stick with the bluing agent rather than fiddling about with different acids jellies etc. Gun blue is made to blue steel. Follow the instructions, light sand back, repeat until desired effect is achieved (or you've sanded through to the other side of the blade. Whoops).

We must remember that we'll never get it back to pristine. These are old tools and more often than not pretty rusty before we get to have a go at them. It is good fun trying though isn't it?

Keep us updated with your progress.

Cheers,
Virg.

I have been mucking about with this today using the brass darkening solution as per Bob Sturgeon. For any one in Sydney this is available from Mother of Pearl and Sons. The saw is a Disston 5. Its the top one:
Attachment 248693
When I started the etch was there but as silver as the saw plate. After 4-5 with the solution this is the result (which i am pretty happy with) :
Attachment 248694

I like it! :2tsup:

What did you do for pre-cleaning and post-cleaning?

Good job PM.

Cheers,
PM.

Pre cleaning was scraped with a stanley blade then sandpaper glued to a block using detergent as a lubricant. That was back in December.

Today i wiped it over painted the stuff on and used 400 wet and dry on a wood block in between coats. W and D was lubricated with G15.

Probabaly need to go back and address some of those cows and calves though. Now that i have seen them close up.

Quote:

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Originally Posted by Pac man

Probabaly need to go back and address some of those cows and calves though. Now that i have seen them close up.

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Proof. Pudding. How does it feel to use?

Cuts a dead straight line in hardwood at 19mm thick and less. Jams a bit in thicker softwood - hardly any set on it.

I think the saw is telling me it will be ok

Quote:

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Originally Posted by Pac man

Probabaly need to go back and address some of those cows and calves though. Now that i have seen them close up.

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Looks pretty reasonable to me! Not much wildlife there. (I think the camera has put a bit of a wave into the photo.)

One of the advantages to hand-filing is supposed to be the natural variations introduced in the process vs machine-like regularity
... like with the liogier rasps & files ...

except with experience ... I assume you get more uniform and regular :)
Hmmm :think:

What sort of filing did you put on it?

Thanks,
paul

Rip. Dont know teeth PPI or TPI as i dint count it. Hardly any set. Fleam?Rake? Just angled the file how the teeth were set in the first place.

Sorry this is probably not helpful. Saw jargon is my third language

Quote:

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Originally Posted by Pac man

When I started the etch was there but as silver as the saw plate. After 4-5 with the solution this is the result (which i am pretty happy with) :
Attachment 248694

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Thanks for the info Pacman. I ordered some from Watson Brass (watsonbrass.com.au) and it turned up today.

The image on the website looks like ...
http://www.watsonbrass.com.au/bmz_ca...ge.214x550.jpg
But what I got was:

Attachment 250025

So, I was on my guard a bit. I tried it on the Spear & Jackson 888 I am working on ... it basically had no effect at all.

It has seen a lot of WD40 and then the Phosporic Acid that I tried on it ... so I will give it a go again tomorrow after I get some acetone to wipe it down with.
There may be something different about the sawblade and etch vs older saws ... see below.

I took one of the saw-chest saws ... a moderate condition #7 ... the bottom one here ... I haven't cleaned it up from then ...
https://www.woodworkforums.com/attach...saws-2-055.jpg

The etch looked fairly reasonable on a less-than-clean saw-blade.

Attachment 250026

This saw has not had any WD40 or etc so I gave it a light sand-over and a wipe, then created a pool of the liquid over the etch section and left for about 10 minutes. Cleaning off the remains, it had created a darkened area on the saw-blade ... much like the phosphoric acid did.

Sanding over the darkened area, the etch was probably enhanced - I haven't made a close comparison of the photos, but the rest of the saw-blade was cleaned or possibly smoothed. In any case, a good result.

Attachment 250027 Attachment 250028

I still prefer hand-rubbing to the sanding-block. For one, you can direct the sanding effort to a few square cms, rather than a hand-sized area - although I guess you could make smaller blocks. Also the sanding was done putting almost no finger pressure onto the abrasive ... and you can lighten up or not at will.

I will also find another old etch like this one ... might use the same one if I have to ... to test the phosphoric acid again.

Thanks Pacman.
Paul.