Precautions for the use of HF Acid – 26/8/99
by Les Lowe
DISCLAIMER: Individuals use this information solely at their own risk. If you are not willing to accept the risk associated with using this or any other acid, then don’t read this article or depend on it’s content. The author provides this information FREE of charge as a public service and accepts no liability for it’s contents.
The best way of treating an accident is not to have one in the first place!! So make sure that the work area that you plan to use is uncluttered. The bench top should be clear of anything that may catch the acid container whilst being moved. The floor area should be clear of tripping hazards – one, you may trip whilst holding the bottle and two, you may have to step backwards in a hurry if you do have a spill. Make sure the decks are clear. Know EXACTLY where the HF acid is located before you start to use it. Know EXACTLY where you will be placing the containers holding HF acid with the gold in it while the nuggets clean up – may take a day (or two).
I know this sounds extreme but wear full length PVC raincoat, buttoned up to the neck, Wear at least goggles and also a face shield over the top of those if you can get one. Wear PVC gloves – NOT rubber ones that they will sell to you at a chemist and tell you they’re PVC.!! PVC wellies are hard to come by, so get a good thick pair of ordinary wellies but ensure that they are of such a fit that you can get your feet out of ‘em rapidly and without having to touch ‘em –i.e. without having to pull ‘em off with your hands. i.e. you can shake ‘em off. If you’re wearing boots or shoes you’ll never get ‘em off quickly enough to prevent the burn. I wear two pairs of gloves one skin tight like medical gloves (hard to get hold of and another over pair over the top.
Have a big container of Bicarbonate of Soda or Calcium Carbonate at hand. Preferably an open neck container. I use a large plastic bag that is wide open at the top when I’m handling acid. That way I can grab a handful quick if I need it without having to piss around unscrewing tops etc. Remember you’ll be wearing goggles and your vision will be somewhat limited. You’ll also be wearing big clumsy gloves and can’t grab stuff real easy – So if you need the Bicarb or the Calcium in a hurry you don’t want to be fumbling around for it.
The container that will hold the acid (and the gold) should be PVC – Tupperware is ideal, particularly their pie dishes etc. This container should be shallow rather than deep. E.g. don’t use a Tupperware beaker. they’re too easy to knock over. Use something that is shallow and stable, and can’t be easily tipped over.
A second PVC container should be made ready by covering the bottom with bicarb of soda. Then, the first container “holding the acid” should be placed INSIDE this container so that it is resting on the bed of bicarb in a stable manner. This container should be taller than the internal one holding the acid. What we are trying to achieve is a “holding system” where the acid cannot readily be knocked over, but if it is knocked and a small spill occurs then the spill will be caught by the outer container holding the bicarb and will be neutralized. If a spill does occur and the HF contacts the Bicarb – stand back, well back- – the fumes will cause your “clack” valve to shut and you will have trouble breathing – besides given long enough chronic exposure (unlikely in our case) HF fumes will calcify your lung tissue.
Place your gold in the internal container – the one where the HF acid will be held.
Have a tube of Calcium Gluconate Gel handy – so handy you can reach it without taking a step. Same with the bags of Bicarb and Calcium if you can mange it
When the “holding system” is ready and bicarb is in there, fix your mind on what you are about to do – don’t be distracted by anything – anything at all!! Tell everybody to “leave you alone “and get away from you and the shed that you’re in. If anything goes wrong – you want a quick exit. I always use my HF when everyone else is out of the house. Use TENDER LOVING CARE just like you did with your firstborn child and take THE BOTTLE OF ACID TO THE GOLD CLEANING CONTAINER – NOT THE OTHER WAY AROUND ( It’s a moral that you’ll spill the container on the way back to your workbench!!). The HF acid bottle, it’s top seal and pouring nozzle are 99% spill proof –your holding system of container is not!!! Do not remove the HF nozzle seal YET.
When you have HF bottle over the top your holding system of PVC containers – CAREFULLY remove the seal and the screw on top. Slowly tip the bottle – the acid will come out in an unexpectedly slow fashion – the nozzle has a restrictor in it – a bit like using Tabasco Sauce- you have to shake shit out of a Tabasco Sauce bottle to get any out. DON”T shake a HF bottle!!! Just let it come out slowly.
Don’t take too deep a breath (the fumes are not a major problem but there will be some and they do take your breath away slightly) and pour the HF Acid over the gold until the nuggets are covered. You can, if you want to, pour only sufficient HF in to cover “the dirty bits” of the nuggets. But be warned that you may end with a nugget that is ¾ “squeaky” clean and ¼ ” natural, just found gold colored”!! The choice is your – I cover the lot up.
Put the screw top back on the acid and take the acid back to YOUR PREDETERMINED SAFE STORAGE PLACE. Make sure the bottle is safe and stable – don’t rush things.
DO NOT – I REPEAT DO NOT PUT A TOP ON THE GOLD CLEANING CONTAINERS WHILE YOU HAVE ACID IN THEM – the amount of fumes that are given off are sufficient to build up and pop the top off a PVC orange juice concentrate bottle. I’ve seen it happen ( after I told the person NOT to put the top back on) and the resulting mini –explosion sprayed 70% HF all over his shed. When we got there, the wood shelves were smoking and the corrugated iron walls had a lot of very decorative smoking holes in it!!! God help any poor bastard that could have been in there when it went off!!!
The HF will fume as it starts to eat the rock etc. These fumes are hazardous and will over a period of months of repeated cleaning of gold cause pitting of nearby steel, such as your bench. It will also cause frosting of any glass containers that happen to be within a few feet. So imagine what it does to your lungs and other parts of your body.
When you are happy with everything and have lost a bit of that nervous tension – well here comes the hard bit – CAREFULLY pick up the “holding system” of containers and place the lot in THAT SAFE PLACE THAT YOU SHOULD HAVE DETERMINED IN STEP No 1.
Make sure that this “SAFE PLACE” is low down- but NOT on the floor where it can be accidentally kicked. The lower shelf of a rack of shelves is best – but not where kids and cats can put their paws in it!! (The cat is personal experience – next doors – I never liked it anyway since it attacked and killed most of my son’s guinea pigs!!)
At the end of the “cleaning period”, maybe a day or two, mix a strong solution of Bicarb of Soda in an wide necked glass or plastic jar- about two liters will do. This is the container into which you will drop the nuggets in order to neutralize the acid.
When the gold is sufficiently cleaned use a pair of PVC tongs – cut down tea bag squeezers are good (Good god – who’d have ever thought that someone can make money out of inventing “tea bag squeezing tongs”!! ) or plastic sugar cube tongs. You can use small steel tongs but they don’t last too long – and transfer the nuggets into the jar containing the strong bicarb solution. They will fizz a bit but don’t worry – they won’t explode!!
Swirl the nuggets around and make sure they all receive good contact with the bicarb solution.
Get a large plastic flour sieve and pour the contents of the jar into the sieve – it’s handy to have another empty plastic jar underneath to catch what is still usable bicarb solution (keep the costs down!!!) and more importantly – catches any fines that may pass through the sieve. The fines should be allowed to build up as you would a “poverty pot” and panned off when the jar gets a bit full or you are real short of cash!!!
Holding the nuggets in the plastic sieve, wash the nuggets thoroughly with copious running water.
The nuggets are now neutralized and fit to be held in your bare hands
WARNING – be very wary of species that come out of the acid still containing some rock, particularly quartz. Quartz becomes very soft and porous after HF. If it’s not all fallen off in the cleaning it can hold trace amounts of acid and it can burn – I know it ‘cause it happened to me. Only a small burn but it stung like a snake bite!!! Leave items such as these in the Bicarb solution for at least another four hours and wash ‘em very thoroughly at the end – OR just wash’ em and then stick back in the acid. If you’re going to put ‘em back in the HF to get rid of the last of the quartz, it’s best to wash ‘em with water first. This washes off the Bicarb which would weaken the acid.
Remember think about what you’re doing before you do it and work out what you will do if it does go wrong.
If you do cop a burn then apply Calcium Gluconate Gel immediately – don’t try and wash it off first and then put the gel on to it. Hit with the gel, then go and look for a tap. Then wash it off and apply more gel UNTIL THE BURNING STOPS. If the burning hasn’t stopped then obviously bits of you are still disappearing!!! Get some medical assistance if the burning doesn’t stop within a couple of minutes. MAKE SURE YOU USE A GLOVED HAND TO APPLY THE GEL. Otherwise you’ll cop it on the hand that’s’ applying the gel!! I’ve seen this happen – done by a trained paramedic!!! And he couldn’t understand what he did wrong!!!
There is such a thing known as a “Delayed Burn”. This is where you get a very minuscule dot of the HF on you and it doesn’t become apparent for some time afterwards. It seems that you get an itch deep in your skin and you can’t stop it. I’ve never experienced this myself or with other people but it has happened. All you can do is apply Calcium Gluconate Gel and go to a hospital.
I think that’s all – good luck – don’t get careless with this stuff it hurts like something you’ve never experienced before.
Any questions – just ask!