Sanding before or after acid?

[plainpainter 217]

Other than the deck I posted about the befores and 16 month afters - I usually end up sanding my decks down. I like it better that way - perhaps it's a better job - and perhaps folks in New England neglect their decks much much more than the rest of the nation - and we have really harsh elements here. Anyways - I got to thinking - if I put on an alkaline stripper followed by an acid bath - then sand. Then potentially aren't I sanding off the top layer of 'conditioned' wood? I mean - if you sand wood enough it becomes 'clean' but wood has 'stuff' in it that may or may not interact with stains. And a brightener seems a good way of sequestering that stuff out of the top layer.

So what I want to know - has anyone experimented with sanding after the stripping stage but before the acid/brightening stage? And did you notice any different results? The more I think about it - it introduces more days on the job and less profitability - but It seemed to me that it may be a superior job - who knows?

[MMI Enterprises 289]

Perhaps better solution there Matt would be to not use RS on redwood unless it is the redwood only version or move yer neutralizing process to being only after sanding. Situation seems good example or basis as well for full on sanding or defur compared to only spotting. It's like obviousely sometimes our wash methods don't always actually remove the dead wood that can actually contribute to making for a pathway the natural extractives/tannins can travel. Mushy dead stuff on top of some woods act like a sponge able to spread the deep stuff at some level but cutting all the way down to fresh wood via sanding makes for like a pure concentrated bleed if that makes any sense right out of vein. In case of redwood it is known that the tannins will bleed from just water alone hence the lighter double neutralizing many us discuss. It is not a cure all though and relates more to finish being suitable or not in my opinion. I say it cause I've tested it.

ps- btw, first neutralizer application could have indeed reached those areas before you sanded them and it would not have mattered..you made a better conduit whether it wet or not.

Edited December 8, 2008 by MMI Enterprises

[plainpainter 217]

I've done a few strips jobs and then brightening - only to come back a few days later and noticed that not all areas of grey were gone sometimes. And my whole reason for this post - is even if I sand down past all the grey - which I have done. Is this 'fresh' layer of wood suitable for staining - or does it need another acid bath to really extract stuff out? I've done decks - where I come back and suitable amount of the stain didn't strip off - and I've spent a whole day sanding everything down baluster and all. Is this sanded down wood as good stripped and then brightened wood?

But as Fenner says - we can go on and on, trying to raise the bar on quality - but in reality what's it going to buy us in terms of longevity - a couple more months? And will homeowner spend 30% for a couple more months? Perhaps if a deck could go 4 years and then only need a maintenance - then it might be worth it to them.

IF anything, sanding has resulted in a more uniform stain finish - with more penetration. And I have also noticed with woodtux - if you strip and brighten and then stain - you will get the 'yellow' pumpkin like tone on pressure treated. But when you sand afterwards - the color is much deeper and richer in tone. And that alone is worth the price for sanding.

[Beth n Rod 1,279]

I think this thread is getting out of context. The only time you will have too do multi- Neutralization and re-cleaning is for difficult jobs that call for it. Which Rod has stated and I haven't even touched upon things I've done.

You are the king of multi-step jobs in ways most never think about! ;)

Beth

[Beth n Rod 1,279]

Well yea we now know Rod sweats alot on decks..lol..What things you done on a deck that top that?...hehe :)

What, you have never seen salt stains on a deck? HAHAHAHA Rookie! :lol:

Beth :seeya:

[MMI Enterprises 289]

What, you have never seen salt stains on a deck? HAHAHAHA Rookie! :lol:

haha.. I wear overalls, hats, and bring my own porta potty..:lol:

[Beth n Rod 1,279]

Yeah but there are other ways besides sweating to see salt stains on a deck.... ;)

Beth :lol:

[MMI Enterprises 289]

I've done a few strips jobs and then brightening - only to come back a few days later and noticed that not all areas of grey were gone sometimes. And my whole reason for this post - is even if I sand down past all the grey - which I have done. Is this 'fresh' layer of wood suitable for staining - or does it need another acid bath to really extract stuff out? I've done decks - where I come back and suitable amount of the stain didn't strip off - and I've spent a whole day sanding everything down baluster and all. Is this sanded down wood as good stripped and then brightened wood?

Gray or unfinished strip is just case for another go at it with same but stronger process. Far as yer question's...yes, should be suitable for staining but obviousley not in all cases such as woods or stains that may not react well together. I don't see the wording 'extract stuff out' as pertaining as for of course when we neutralize we are meaning to just change the ph. Of course when the solvent getting the neutralizer in there is water then we can have them other issues of darkening or bad stain response. Besides that, what else could be issue other than sanded area taking stain differently if not better. That said, differently doesn't necessarily mean superior.

[MMI Enterprises 289]

Yeah but there are other ways besides sweating to see salt stains on a deck.... ;)

Beth :lol:

Well this salty dog shows his deck some salt every day and it is same color 30 years in....lol :lol:

ps- not sure who here is more in the gutter.. lmaof

[Beth n Rod 1,279]

Well this salty dog shows his deck some salt every day and it is same color 30 years in....lol :lol:

ps- not sure who here is more in the gutter.. lmaof

Pottybrain...

Must be you, because I was not in the gutter at all. I was referring to not rinsing the deck after neutralizing and having the salt residue show up when it dries. It can happen. I've seen it.

Beth

[MMI Enterprises 289]

yea but you said it like twice hence implying other perhaps more gutter minded methods that probably only James himself could dream up?.. :)

[Beth n Rod 1,279]

yea but you said it like twice hence implying other perhaps more gutter minded methods that probably only James himself could dream up?.. :)

Oh no you don't, I didn't imply anything of the sort. You're on your own pottybrain!

Beth

[MMI Enterprises 289]

granted..now if we could flush the potty posts we could get back on job.:)

[RPetry 564]

.... I was referring to not rinsing the deck after neutralizing and having the salt residue show up when it dries. It can happen. I've seen it.

Beth

Beth,

This must be due to oxalic acid and/or mix concentration. Using straight citric acid at 6 - 8 oz./gal., we have never had any noticeable residue, salt or otherwise, on decks we prep. Using RS, we never rinse the brightener.

Will second Jim and Matt's experience. Redwood and cedar are challenging woods to stain evenly after a hard sanding. A second app of brightener, specifically a specialty brightener in the case of belt sanding a floor, is best.

[Beth n Rod 1,279]

This must be due to oxalic acid and/or mix concentration.

DING DING DING DING!!!!! Rick gets the prize! :banana: :dancing:

We have actually been called by home owners who have had this phenomenon on their deck after getting it done my another company and the contractor had no clue what it was or how to fix it. It's a great way to get a new customer. ;)

We don't use straight OX, we like a blend and have not had this issue when using a blend. Have seen some really messy looking decks though.....

Beth :seeya:

[PressurePros 249]

When an acid is combined with a caustic, a salt is formed. Extensive rinsing should be the final part in any chemical restoration/cleaning.

[Beth n Rod 1,279]

We get that...there are folks who do not rinse...that was the point of pointing out the potential for residue.

Beth

[Beth n Rod 1,279]

Here's an oldie but a goodie... http://www.thegrimescene.com/forums/library/50-please-pass-salt.html

Beth

[MMI Enterprises 289]

Too much exageration going on in my opinion about salt. Feel free to let me know what ya think...

Not a chemist, so but the way I see it the main 'potential' to make problematic salts would be the starting concentrations of the metals (NaOH) and acid (which ever acid). In the course of cleaning or stripping we are already rinsing the main doses of metals with 5gpm+ before acidifying the wood. I say acidifying as the normally used word in neutralizing is usually incorrect by way of the very nature of being able to go lower than would be expected from an equivelance/balance of both the acid and base involved. In the case of decent flushing of wood with oxalic (ethanedioic) acid you bypass neutral and haven't much chance of forming it's ions into salts. You aren't going to be making a buffered solution. If overwhelming amounts of salt had been formed said salts would buffer the overall ph solution preventing further acidifying. But generally it doesn't happen and I've never seen it on a deck and don't expect to neither. Note in Russell's thread there can be found confirmation that the process involves the acid going neutral. If you try to do a titration you would have to add back some alkaline cleaner to the acid to reach equivelance point.

..take a petri dish in a lab situation and place a sponge in it. Now dose the heck out of it with a titration indicator mix of hydroxide and phenolphthalien until full. It will be a redish pink color. Run it under faucet for hardly any time similar to rinsing stripper on a deck and it goes clear. Now flood dish/sponge with a oxalic solution. It won't go red.

On the acidic redwoods I deal with the effect is even that much worse in trying to make something of salt when you get down decently into fresher wood by way of cleaning or sanding.

Realize further that on yer darkened wood or yellowed wood you are pretty much looking at end effect rather than current situational amount of chems within. Confirm this by rinsing the wood for hours on end with neutral water..it'll never turn color until you brighten. btw same can happen on carpet and solution is something called brownout if I remember correctly. Example of the flip in color or brightness of wood is not really akin to titrating in my mind.

All that said yes it indeed possable that at some point any of us may leave some alkaline chems in wood by way of insufficient rinse and set ourself up for problems with a stain reacting badly or some salts being formed that don't flow away. I mean we are after all by nature of the equipment driving things into the wood and then relying somewhat on things mixing or absorbing by way of water solvency or Ken's mention of surfactance. Hey 2 stepping probably makes some salt eh?...

Here's some ref that points out speed of ph lowering/buffering and perhaps is something of confirmation of some the points I make:

pH curves (titration curves)

"Titration curves for weak acid v strong base

We'll take ethanoic acid and sodium hydroxide as typical of a weak acid and a strong base.

Running acid into the alkali

For the first part of the graph, you have an excess of sodium hydroxide. The curve will be exactly the same as when you add hydrochloric acid to sodium hydroxide. Once the acid is in excess, there will be a difference.

Past the equivalence point you have a buffer solution containing sodium ethanoate and ethanoic acid. This resists any large fall in pH."

edit: correction though- above acid is acetic rather than oxalic..spelling is similar so no they not specifically talking of our oxalic example but just the same ya probably can still see the points and it suitable example.

Edited December 9, 2008 by MMI Enterprises

[Beth n Rod 1,279]

I've seen the salt residue. That's all I'm saying.

And people find it unsightly when it occurs, especially if they just spent a bunch of money to have a nice clean and freshly sealed deck, not a clean sealed deck with residue on it.

Rinse...rinse...rinse.... ;)

Beth

[MMI Enterprises 289]

yup..that what I do..rinse rinse rinse, especially during strip and yup even sometimes during brightening. :)

[RPetry 564]

Holy smokes Kevin, friggin' graphs, formulas, the whole nine yards. Chemistry is not my strong point. But a good rinse, ie: using your PW when stripping with NaOH or sodium percarb may very well negate any chance of "salts", whatever that is, forming with a reaction with an acid.

Is this what you are saying in plain English?

All I know is that many RS users, for years, have not rinsed off the acid neutralizer/brightener, with no ill effects. In fact, it has been postulated by others that a slightly acidic wood surface may actually be better for a straight paraffinic oil stain.

Don't know about that, all I know is that 7 yrs. of RS, citric acid, and not rinsing works well for us and our customer's wood.

[plainpainter 217]

I have always personally thought that oxalic acid in quantities of 8 ozs. per gallon should be applied directly to dwelling stripper - instead of rinsing stripper first. I haven't seen any evidence either that after you really rinse stripper - that there is anything left to 'neutralize'. I think the neutralization is more for sequestering the tannins out from the wood to get it back to a more pleasing color. But the above method - would negate one rinsing - thus saving time.

Don't believe me - try this for an experiment - soak your deck with your favorite sodium hydroxide based stripper - just before you rinse - apply your favorite percarb cleaner, whether it's efc-38, F-10, or 3/4 cup oxiclean & 1/4 cup TSP per gallon. Apply it to the dwelling stripper. You will immediately see the wood brighten right up - not as much as applying acid - but brightens nontheless.

[MMI Enterprises 289]

Yup that's pretty much the English of what I sayin Rick.

Other than that..RS has been fine with yer wood so go with it.

Even though the rs site itself has some info or reasoning of their redwood only version I do know the aspects of the wood west versus the east of the big Miss can rightly be downplayed compared to either excessive extractives found in old time heartwood or redwood being rone in general. Heck it could be just that any fresher redwood no matter where from could respond badly to some standard formula. I heard the redwood not all much different these day whereever it comes and yet I've seen it go black. Just my experience with it is all on new boards which should be directly comparabel to what Matt said of his sanded wood.

[MMI Enterprises 289]

I hear ya Dan...

that there is anything left to 'neutralize'.

Just as easy this statement can mean there nothing left of base to take the acid to neutral.

One reason I suggest staying high enough on acid mix is that if yer way weak and you do have some base still present than yer bound to end up making some salt...same fer only lightly misting a deck wth pumpup..

If yer gonna do such a mist then perhaps it is best after a main flush of acid and mainly designed to get rid of persistant dark areas or tannin moving around..

[James 625]

I think the point we are missing here is removing the finish. Sometimes we are doing multi- applications of a strong Alki. Deciding when to stop the alki action is another matter. Has the Finish been removed? Do we need to to do it again? Do we want to stop the action of the Alki? Do we already know we have to sand? Is there allot of organic Stains, Rust stains ect..? Is there a need to Bleach the wood after stripping?

Stopping the action of the Stripper and Removing Tannin Stains and Brightening the wood are different actions although many or most times a simple neutralization works after a clean or mild strip of the wood.I do know the less moisture that is in the wood the better the Acid works for removing Tannins and Stains.

When using OxAcid a problem happens when it doesn't totally dissolve and it leaves a Salty looking resydue on your woodfriendmembers deck. Or Rod has been on your DEck working out to the Oldy's

If I keep on writing do you think I'll give Kev a Headache because I have one ? LOL