Caustic Soda

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Does anyone know how to mix and use caustic soda ?
After sanding away at coving I found that rather than being plaster it is actually wood. I thought it would be nice to get it back to it's original state. I've removed most of the paint with a hot air gun and then gone over with Nitromors but there are still some stubborn patches of paint embedded in what seem to be small gouges in the wood.
I've got some industrial strength caustic soda from a local brewery but I don't know what quantities to mix, what to apply it with or how long to leave it. I've tried a bristle brush in a sample solution but it lasted only a short while !!!
Thanks in anticipation
Martin
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Martin Robbins wrote:

Please be extremely careful with sodium hydroxide (caustic soda or 'lye' as our Americans friends like to call the diluted form). Avoid any skin contact (PVC gloves are a must) and wear goggles. Believe me - it can be lethal - I cannot stress too much the dangers of this substance. It's highly alkaline, very toxic and can strip the skin from your fingers - also avoid any inhalation. If you must use it, add very carefully to COLD water (it generates heat), stirring constantly and avoid contact with zinc or aluminium and certainly anything acidic. Is this a solution you've obtained or the solid form or in pellets? As an ex industrial chemist, I've handled both, but again I must stress the safety aspects. Please don't mess with it. My advice is to dispose of it safely (take advice) and think of another method.
Terry D.
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Terry D wrote in message ...

heat you describe has subsided. You could wash your hands in it providing you got it off quickly. The danger is *prolonged* contact with skin. Get it inside your gloves and you can peel back your finger nails to the quick after half an hour. Using it overhead on coving would be very messy but, if you insist, get a synthetic bristle brush and put some tape round your cuffs. The stuff you're trying to get rid of from the grain is probably filler, which even caustic may not remove. The main advantage is that it changes the look of the wood and IMO improves it if you're looking for an antique colour. You can sort of thicken caustic soda with flour. Dissolve the flour in water first. Still slops everywhere but that's the nature of the beast.
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It's in a sort of crystal form, a little like salt. I noticed it generated heat.

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Martin Robbins wrote:

supplied it to you in in the first place. Believe me , you don't want to mess with this stuff.
Terry D.
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Terry D wrote:

Keep it for drain clearance. You can buy solid NaOH from most hardware shops anyway.

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I buy 20 kg bags from an electroplaters for 8, using it before it solidifies is a bit of a problem
--
geoff

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I've been using quite a lot of it recently in the biodiesel process - I've found storing it in a plastic barrel with airtight lid and clamp helps a lot in keeping the moisture at bay.
--

Dave

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Lye is the old English word for it. It was made by pouring water through wood ash, still is by those who demonstrate mediaeval soap making, like me!
Mary
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On Sun, 26 Oct 2003 21:05:48 -0000, "Mary Fisher"

Soda lye maybe

Potash lye

Soda lye makes a harder soap than potash lye, no idea if there is any difference in their cleansing ability.
AJH
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Andrew wrote:

I can't see why it should, since the active part of the soap is the organic acid ion. Unless using the different hydroxides leaves differing amounts of the original ester in the resulting soap.
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All that had no relevance to our mediaeval ancestors. It cleaned clothes, that was the only criterion.
Mary
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Terry D wrote:

My goodness - that's a warning and a half! I feel you're scaremongering a little.
Sodium hydroxide is a strong alkali, and will strip skin and damage eyes. But so will boiling water, and we all handle that every time we make tea. A splash of concentrated sodium hydroxide on your skin will not do any damage as long as it's washed off straight away. Just be careful using it and you'll be fine.
As for the heat generation, pellets dissolve at such a slow rate that the heat is generated in a very controlled manner. Just don't dump a whole load of pellets in a small volume of water all at once.
I commend the brewery for their helpfulness - getting hold of useful materials is getting increasingly difficult, unless you work in a lab.
--
Grunff
(who has spent too long in labs working with far nastier compounds)
  Click to see the full signature.
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My sentiments exactly.
I use it from time to time, and as long as you take sensible precautions, you should be OK
Get it on your skin and it itches, but I've never had chunks of flesh peeling away yet.
The heat generated by hydration can be quite severe, so add crystals slowly and take precautions against getting splashed.
Lastly, it is hygroscopic - keep it dry or you could end up with a bag full of one big lump of sodium hydroxide
--
geoff

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It's actually deliquescent. Wait long enough (not long in this weather) and you'll end up with a puddle of saturated NaOH solution. -- Die Gotterspammerung - Junkmail of the Gods
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There is no doubt caustic soda is dangerous but everyone here is an an adult and responsible for keeping themselves safe. One thing I would say is that as a childrens nurse I have seen horrible effects when a child put a single chrystal in their mouth (the chrstal had fallen on the floor when dad was mixing it). The child did such damage to their mouth and wind pipe that they now have a tracheostomy and will face years of painful surgery just to get some semblance of normality back.
I agree with Terry, use something else if you can, if not for goodness sake store it safely and be careful how you handle it.
AK
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on what data do you base that assumption?
--
dave @ stejonda

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A K wrote:

That's ridiculous.
Preventing accidents involving children is not achieved by not using things, it's achieved by being careful with what the child has access to.
How many children have you seen with severe burns resulting from boiling water? I don't see you advising people to avoid using kettles and saucepans - or perhaps kitchens altogether.
--
Grunff


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before replying. I didn't say not to use it I said use something else if you can, and if you do use it be careful. The guy had stored it carefully, but had not realised that a chrystal had fallen on the floor. IMHO it doesn't hurt to just to illustrate that accidents can happen

same - BE CAREFUL. There is no alternative to water but there is alternatives to caustic soda and they should be considered.
AK
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A K wrote:

Exactly - "use something else if you can". Why? How does that help children? One good alternative to sodium hydroxide for paint stripping is methylene chloride based stripper. Is that a safer alternative to sodium hydroxide? Most would say not.

The problem is that your assessment of the danger posed by sodium hydroxide is based solely on the incident you described, and not on an understanding of the effects of sodium hydroxide, the alternatives available and the risks associated with them.
Your statement "use something else if you can" implies that anything else is preferable. This is far from the truth. Stripping paint by definition requires a violent process, whether this is mechanical, thermal or chemical. Whatever you do will have risks associated with it. Sodium hydroxide is probably one of the lowest risk options.
--
Grunff


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