Home made laser marking fluid / spray

Metal, Wood, ... the heavy stuff can be found here
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Home made laser marking fluid / spray

Post by Downunder35m »

Unless you have a really powerful laser or a dedicated fibre marking laser things can be tricky on metal.
The rescue comes in the form of laser marking sprays.
Thing is that those are ridiculous in terms of their price.
On a hobby level some people like to use Molybdenum dry lube spray.
Both provide a black(ish) marking with the genuine product being deeper in black and more uniform.

So why do they both work and why do they work so differently?
For hobby use the dry lube is just fine but if you want some nice looking text or logo on something you created for sale ....
The dry lube uses Molybdenum Disuphide while the proper laser marking spray uses Molybdenum Trioxide.
The disulphide is roasted at around 600°C to turn into Molybdenum Trioxide ;)
To get a better result the dry lube should be applied slightly thicker than what is require to get an even coverage.
Then you engrace the are with several passes at high power.
Preferably with no or very limited air assist if the stuff tends to blow off.
You will get close to the quality of the original but not to the finish line.

The disulphide is available for purchase from the usual chemical suppliers and COULD be roasted at home.
But it is a hazardous and energy wasting process.
I tried on a small scale with just about 15g of disulphide in a tiny crucible and using a blow torch.
If you have a proper kiln and good sized crucibles at hand you might be able to produce Molybdenum Trioxide quite cheap with reasonable purity.
It requires though to keep the temp below 650° to prevent the stuff from clumping up and you need to agitate it so all can oxidize.
With the health hazard of the stuff it not something I would look forward to.

On the other hand and although still very expensive we can buy the Molybdenum Trioxide directly.
Lab quality comes as fine crystals of usually yellowish color - a bit like fine table salt.
Techincal grade Molybdenum Trioxide is much cheaper but comes with various crystal sizes in the same container.
Purity levels can be ignored for our purposes.
Thing is that we can't really create a "pigment" paint - we don#t want any binders or fillers as this can ruin the results completely.
And the stuff does not really like to dissolve in the usual solvents.
Unless of course we include the most basic solvent we have - WATER.
Sadly that does not really help us that much :(
Even a concentrated solution in hot water causes a problem when used as paint - it takes forever to dry and the PH can be problem on certain metals.
Adding Ammonium Hydroxide certainly improves how much we can dissolve in the water plus it helps to get the PH back in the neutral zone.
At this stage we could just add some thickener like gum arabic or gelantine to get a brushable consistency...
Sadly in my experiments it turned out that water based paint takes rather long to dry...
And on polished metals it can be tricky to get an even coverage.

While my brush on results with the little diode laser were not too shabby - I wasn#t happy with it.
Sure, you could see what was marked but it had a severe lack of consistency.
Some areas dark black, others only slightly grey and a few spots with the metal shining through :(
So I thought "Why not try to make it a spray paint?"...

Thing with spray paint is that you need a spray gun - or at least some cheap airbrush gun.
Those things prefer the thinner paints as otherwise you need a rather big nozzle size and lots of air.
As I did not have ultra fine dust I had to somehow turn those crystals in fine enough "paint pigments".
I wouldn't mind a bit a bit of mess or dust as I could do this outside but the health hazrds if inhaling the powder....
So I took the bullet and paid about $100AU to have 50g of lab grade Molybdenum Trioxide delivered from a local chemical supplier.
Wasn't really dust like but at least a fine enough particle size to consider mortar and pestle.
For this I placed a small garbage bag over it so keep possible dust contained.
As the stuff isn't really hard it is quite easy to turn it into very fine dust this way.
I then put my Covid mask on and removed the bad after letting it settle for a few minutes - outside of course.
Carefully removed all the find powder to get into a small jar.
Tossed in a mixing bar and placed it on the magnetic stirrer after adding a bit of acetone.
That mix applied with a smlaa airbursh gun resulted in almost identical results to the costly marking spray.

Ok, I know what you are saying now....
80 bucks for just 50 grams while a can of dry lube is yours for about 50 bucks and comes with around 300 grams....
Does not sound like a good deal at all - or does it.
For the dry lube we get about 3% of Molybdenum disulphide - for about 300g it makes only 9g ....
The marking spray comes with about 4-5% of Molybdenum Trioxide per can, so not really much more either.
If we make it a generous 5% than 50 grams of crystals you turn into "pigments" will make over 1.5 liters.....
As I know how hard it is to get this stuff in small quantities, most would have to opt for the 500g variety.
And here the price is about $1AU per gram.
If you now wonder what to do with about 1000 liters of laser marking fluid then I couldn#t answer this...
But I could say that if you use just 5 cans per year of the real deal you would already make a good saving....
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

If you want to know why real marking spray is soooo expensive we have to look into the ingredients.
We know the Molybdenum Trioxide is the main one.
But we also find Acetone and Propylene Glycol in most of them - to act as a transport medium and surfactant that dries of reasonably quick.
Needless to say these would only make up for at most 5 bucks worth of the product.
There is of course also the can....
The real cost factor though is those "remaining" ingredients they are not required to specify.
It is like with all spray paints really.
Compare the results froma 5$ can to brand name that costs 20 bucks and you know what I mean.
It is not just the much faster drying time ;)

With just the pure basics, being Molybdenum Trioxide, Acetone and a little bit of Propylene Glycol (Anti freeze) the result in terms of coverage being even, nor mess and so on are really acceptable.
The adhesion not so much - once dry it just smears off with ease.
Since we value our lenses and use at least a bit of air assist this can turn into a problem, especially on polished surafes.
I found that adding a tiny amount of citric acide really helps with the binding and initial wetting of the surface.
However the abresion resistance of the marked area is rather poor compared to the original.
Almost as if not enough penetrates the surface.
Main problem though was a different one.
I required at least 5 passes to get a cover that resulted in a good level of black on the engraved areas.
This WILL get rather costly if need to cover a big area to do a lot of text rather than fully engraving it in black.
With the drying time between the applications it was also rather time consuming.

I prefer one or two passes with a longer drying time ofe 5 to 7 passes...
But how do you get more "paint" per layer if the stuff is so runny ?
You guessed it...
Either we need to increase the Molybdenum Trioxide volume in the mix or we have to make the paint thicker to be able to deliver more in a single pass.
And while I was claening up the last mess I contemplated over how to get this one done.
Until I checked the paper cloth I used to clean the piece with after the last engraving - it had a lot of black on it...
The metal should turn black through Molybdenum binding to the surface.
But a good portion of it seemed to have been just loosly deposited with no binding to anything.

Right now I assume this happened because the powder was still not fine enough.
While the surface looks a bit like you applied some zink spray in terms of texture all this texture also reflects and driffuses the laser light.
So I guess I have to make another batch and try some different spped and air settings so the coating has a chance to heat enough to melt so the chemical reaction with metal to be engraved can happen properly.
Maybe I just rushed things too much at 2000mm/s....
Will get back to you on that one!
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

Ok, progress was made :)
I managed to powder a few grams.
Used a fine filter screen to remove whatever was still too big in particle size, which was quite a bit.
The remaining powder I mixed into about 50 ml of wam methanol with two table spoons of boiling water added.
A knife's tip worth of sodium hydroxide was added as I ran out of ammonium hydroxide.
This resulted in about half of the powder being dissolved.
To prevent the rest from just sinking down quickly I kept adding tiny amounts of xanthan gum while stirring it with the magnetic stirrer and a roduntil the crystal kept mostly suspended.

Why the xanthan gum?
Well, it provides the magic consistency of getting runny with agitation while turning firm when resting.
It also help with the binding when the mix dries on a surface to be engraved.
In the tiny amounts required it does not impact on the result or charring too much either.
Main reason though was to see if this mix is finally good enough to be brushed on rather than spryed on.

To my surpise the result looked rather great.
A full black and the usual stink while drying and engraving was much reduced as well.
Scratch resistance was acceptable with metal polish having no real effect on the engraving.
Another thing thatis now subject to further testing is the recycling aspect.
While the brush on approach did work reasonably well I still have to do some tuning on the consistency.
Since the solvents evaporate and the dry gum dissolves in water with ease it should be possible to recycle and re-use the unangraved coating, probably even what might come off the engraved areas during the cleanup.

So yes!
You actually can make good quality marking paint / fluid at home.
It IS costly though if you can't get the Trioxide in small quantities.
Next step is to test alternative ways to deposit the Trioxide onto the surface, like using tape or a mini duster.
With the right solvent / binder combo it should even be possible to use a rubber roller to get a uniform coating with the lest amount of waste.
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

What else can we do?

Well, if we assume Molybdenum works so great because it is also used in many allos we could assume that other metals salt should work as well.
Like Chrome or Vanadium.
Thing is that the salts we might be able to use are even more harmful than this Trioxide.
I guess it comes down to what sort of result we expect in terms of durability.
Laser toner certainly does work if you get the layer thickness and power right but it is not actually fused with themetal, just stuck to it like paint or wax.
I found some little reasearch paper discussing the effexct of hydrogen peroxide added to etching solutions.
That proton exchange is highly volatile...
And those marking fluids use a TRIOXIDE - meaning three available Oxygen atoms involved.
What exactly happens with that highly corrosive oxygen ? ;)

If we could have a metal salt AND oxygen provider we "only" need to find those combinations that won't start to burn, are highly corrosive and preferably not harmful.
On the other hand we could use a (colored) ceramic powder with a binder aggressive enough to etch the metal in question while also acting as a catalyst allowing the ceramic to bond the metal through the heat and chemical reaction provided by the laser.
I think one day I will try laser copper plating ;)
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

I made a stupid decison :)
I ordered more trioxide and will try to make a small batch of my own recipe to sell online.

Right now the plan is to provide a brush on solution rather than a spray.
But it should be possible to use it in a small spray gun for bigger projects if need be.
Once the new batch arrives I will try to find the right mix and take some meaningful pics and maybe also a some videos showing the cleaning and polishing tests.
If you would like to be a beta tester when the mix is ready then please leave a short note here and I will get back to you once ready.
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

I finally figured out how to properly and fully dissolve the trioxide :)
On top of that I even found a neat way to the stuff burshable and sprayable.
Only thing I really struggle with is finding a cheap option to get it into my own spray cans :(
Cans from China cost about 20 cents each but you need to order at least 1000, at least 2000 if you want some logo or such on it at extra costs.
These fancy refillable spray cans go for at least $60 each and might be nice thing to have as a promotional gift but not for larger amounts.
I guess I will settle for brushing and optional filling it in some paint sprayer or airbrush gun.
Every proper workshop should have the former or later somewhere ;)

Only real problem left righ now is the drying time.
At the about 18° I keep inside it takes about an hour to fully dry to be ready for the laser.
Of course higher temps speed things up but still.
Would like to get it down t no longer than 20 minutes.
The methanol I used to cheat here turned out to be a rather bad choice in terms of long stability of the product.
Who would have guessed the Trioxide actually oxidizes the methanol....
Similar thing happened when trying Acetone - over time the product breaks down.
Would still make for some good dry product you can mix ready for use but that is too much of a hassle.
I need to either find a stabilizer or some quick evaporating stuff that won't react with the trioxide or other ingredients.
If you are not in a big rush though the stuff already works rather great.
Will see that I do some meaningful pics next week.
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

I though I seek some local help on this project of mine.
After work I popped in at a company in town doing commercial laser engraving.
Sings and such for business and councils.
For this I filled my last test batch into the can of my spray gun and was rather hopeful.

Explained to the nice girl at the reception why I am there and whether or not I could talk to someone about my home made laser marking fluid.
Was pleasently surprised to hear the boss himself will offer some of his valued time for me.
And so I stated how I would like to produce a good laser marking fluid at a much lower price than any of the available solutions.
Of course also that I would like to have someone doing this on a professional level evaluted the stuff for an honest feedback.
We grabbed some scrap pieces to spray the stuff on and funny enough the had a heatedtable for this purpose LOL
Anyway....
If I trust his words he was rather pleased with the outcome on stainless steel, tool steel and aluminium.
That was after running quite a few pieces while finding the best engraving settings.
Turns out on their fibre marking machine my stuff requires far less energy to get results...
My hopes were shatter shortly after though when I was told they already have a supplier and that due to the nature of their business and roducts they won't risk swapping products - even if the price would be better.
And well, if it does not come in a ready to go and rather wasteful spray can it is no good...

So tomorrow it is another dash to the scrap yrad to swap the wasted pieces for some fresh material.
Maybe a proper brush on solution is the best way to go for now.
At least more people on a hobby level might want to give it a go.
Why waste over 100 ucks on a brand name can if for half the price you can get more than that coverage? ;)
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

Scrap yard was closed :(
Had to use what I had around.
Image
That was a wet test on a knife.
Wet meaning the solution was not left to dry.

Image
Razor blade after the engraving, again wet application.

Image


Image
The above two are on mild steel.
First is with a purely alcohol based solution, second with added surfectants.

Image
This the razor blade after engraving.
Seems high carbon steel is not ideal, or a single, thin coat wasn't enough.

Image


Image
The two mild steel ieces after cleaning.

Image
This one was some on sandblasted (frosted) stainless steel.
this sample was fully dried before engraving it.

After all I am rather pleased.
A bit of fine tuning and off we go :)
With the drying no longer being that much of a problem things are look good to go ahead.
The "lines" in the mild steel are due to being old and me not giving it a proper polish first.
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

Oh, I forgot the settings andhardware - OOPS...

The engravings were done with a 15W blue laser.
Speed for most was 1000mm/min with 90% power.
The mild steel was done at 2000mm/min and again 90% power.
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
Laser-sculpter
Posts: 914
Joined: Sun Aug 16, 2020 5:32 am
Location: Australia
Contact:

Re: Home made laser marking fluid / spray

Post by Downunder35m »

I did some more tests last night - due to the lack of alternatives on aluminium foil....
As I started with several formulations to figure out which might work best I would like to update on the progress...

My first batch was a mix of Molbbenum trioxide, citric acid, Sodium Hydroxide and Sodium Silicate.
Goal was to abuse the silica for a more durable finish.
Turned out that adding silica to the mix did not improve on the already great durability.
But it produced a very thick and texured engraving.
Almost like a sticker in thickness, you could feel the difference easy with the finger.
I abandoned this mix for now until I figure out how to reduce the roughness of the surface.

The second batch was more traditional.
Trioxide, Sodium Hydroxide and stuff to increase the visocity to a more paint like texure.
Here I neutralised the solution by adding a small amount of Hydrochloric Acid until the PH was back around the 7 mark.
The result was a deep black and lasting finish - unable to be polished away by metal polish.
Unfortunately it wasn't really good in wetting the surface.
Decent preperation of the metal is vital as I found out here LOL
Another piece that I cleaned properly turned out rather well, almost like laser print on paper.

But, up to there, I still had the issue of the Trioxide NOT dissolving fully.
This meant using rather exessive amounts of chemicals and solvents to get it all dissolved, then heating it to reduce the volume back to the target range.
Very time consuming and hazardous in terms of the constant handling required.
I then found a much easy and cleaner way to dissovle the trioxide without the need for the Sodium Hydroxide.
Oh it felt so good to have this lightbulb moment....
Until I relaised that was is really great to dissolve the Trioxide isn#t good at all when it comes to working with binders.....
Increasing the viscosity so the solution is not just like water was hard.

My third batch was based on the fully dissolved Trioxide, Citric Acid as a wetting agent and an emulsifying agent that got a tiny drop of baby oil added.
Drying time was much batter than previous batches but the engraved results were just not acceptable.
The oil of course refused to fully dry, which was intended to provide an even level of crystallisation.
But it made a terrible amount of smoke despite the tiny amounts and made the engraved surface rather "fluffy" - it felt extremely rough.

Next on the list was a batch where I only added Methanol and Citric Acid to provide a faster drying time.
And it was with this batch where I noticed the fundamental problem I had not noticed with the other batches.
The Trioxide does not really crystallise properly.
If you ever tried just normal saltwater you see how it dries up evenly to leave a fine layers of mostly evenly sized crystals behind.
For some reason this was also the first batch to end up in the expected yellowish color once dry.
The other batches always resulted in a more greyish color in some areas.
After reading an awful lot of research papers I figured out the color is due to crystal size and water content.
Water free Trioxide is more grey in color, especially if dust fine.
A bit like Copper Sulphite - without water is pure white, but with water in the crystals it turns into this nice blue color.
And it seems that having this crystal water makes all the difference for the result.
Big problem though was that the Trioxide oxidised the Methanol rather quickly.
Not 100% what the Trioxide turned into but once the solution was getting a bit old the engraving results got worse and worse.
So I started to find a suitable thickening agent to be able to remove the Methanol from the mix....

Problem with thickeners is that drying times go up while it is not always easy to get a uniform coating on the surface.
And of course not all work with something as harmful as Moybdenum trioxide - they break down...
It is quite disappointing when you think you found a great solution that produces good engraving results but see how it breaks down in the tiny jar shortly after.
Thing is that organic binders like food thickeners still break down.
Takes much longer but no one needs a solution that has to be used up within a few days.
Plus: In many cases even the tiny amounts required to create aslightly thicker coating burn away and cause a very rough surface finish.
I still think that there are cases where this actually welcome but if the paper towel leaves a fluffy mess behind when cleaning you know it is too rough for most application.
MOST but maybe not all!
As it turns out this black coating turns rather slippery if abused as a friction surface.
Rub a big steel ball over it with good pressure and you end with a nice non slip surface once "polished".
Did not do a long term test but it seems to be rather durable and might be a viable option to provide long lasting lubrication on a dry surface.

With things going worse no matter what I tried I reverted back to the one thing I knew would not be affected by the Trioxide - Sodium Silicate.
Every tried to mix a Sodium Silicate solution with a highly concentrated solution of something else ? :(
There is a reason it is used to create crastal gardens for chemical experiments our kids can enjoy...
Another problem is that the solution has to fully dry first to prevent the water boiling off from creating this very rough surface.
So far the only feasable option I found is to dilute both solutions before mixing and then simmerning it down at around 80°C for several hours.
Boiling is out of thequestion as then the vapour will contain Trioxide and I don't really like breathing it in for some weird reason...
Still working on the best ratios and by how far it can be reduced.
At least there is progess and the results already looking very promising :)
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Post Reply

Who is online

Users browsing this forum: No registered users and 0 guests