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 !!!
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.
A bit OTT I think. A 10% caustic solution is pretty tame after the initial 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.
My advice is to take it back to the brewery, who really shouldn't have supplied it to you in in the first place. Believe me , you don't want to mess with this stuff.
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.
Oh well. I use it on crystal form, and break all the rules, except the one that says never get it on your eyes.
In my 6th form chemisty class teh not-very-bright boy of the class
managed to suck a cc or so into his mouth using a pipette.
Washed out with gallons of water.
I regularly get it on my skin. It turns the skin into soap. Wash with lots of cold water.
It rots jeans very quickly.
I have even poouyred boilig water on it to get a really superheated hot solution for drain blocakges. Yes, it boils fiercely and splashes boiling hot concentrated alkali everywhere. No, it hasn't killed me yet. I'd rather handle that stuff than a router or planer franjkly - come far nearer serious accidents.
Application of it is tricky. You need a brush that won't be attacked. Most will be. Any drips will wreck whatever they fall on. sso its nopt an ideal solution (haha) for paint stripping - you are probably better of with nitromors and a (electric?) toothbrush. That's not so good on skin either, and a nono for eyes - wear glasses at least.
Caustic is fearsome stuff, but its not instant death the way a chainsaw can be. The antidote is gallons of cold water INSTANTLY on anything that gets splashed, and a very weak acid like vinegar *afterwards* can get the Ph balanced.
I don't think its right for your application, but I think the respondee here is being over cautious.
You might try mixing the solution -once you obtain it, into some lime. The paste should be easier to handle at least. I imagine caustic would be no kinder to flour than it is to skin and brushes.
Have you tried a mild acid such as vinegar on the filler. If it lime based that should ruin it shouldn't it? No idea about that though. Nor what to use to make a paste of it.
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.
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.
I remember a lab technician who preferred not to wear gloves when dealing with the nasty chemicals in a semiconductor lab (stuff much worse than caustic soda). His logic was that with latex gloves, a pinhole or tear could go un-noticed, and you could have nasty stuff (like HF) on your hands for a long time before you notice (hands invariably get sweaty in the gloves anyway, so dampness not a clue), whereas without gloves any splashes would be noticed and remedied immediately. Seemed to make sense.....
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