Brass experiment

[BradG]

Granted, the result of the above looks hideous. Though on a plus side i know why.

My aim is to make a diving rattle out of brass, such as the one i recently posted made from aluminium. the snag here, is that i cant anodise brass. So the plan is to etch it.

For those who dont know, Etching is using a corrosive substance may it be liquid or dry (commonly gas) to corrode away unprotected metal. as you can see in the pic above, everything was protected apart from the letters which were left as bare brass.

Here's the process i used:

three vinyle letter stickers were placed onto the piece

The whole piece of brass was sprayed in photoresist coating
(This is used for protecting copper boards in manufacturing printed circuit boards. this is not a good idea so i found. more on that later)
I then peeled the letters off which exposed the bare brass underneith.

I made a solution of ferric chloride 70%, to 30% distilled water, and placed the piece in at room temperature which was around 23'C

after 1 hour, it had corroded to a depth of 0.1mm in one hour. I predict i could have increased this depth per hour, by regulating the temperature to 35'C, and agitating the solution with bubbles from an airstone and pump.

The issue i encountered is that the photoresist spray was quite jellyfied as it didnt adhere too well to the metal, resulting in me spraying quite a bit on to ensure i had a good coating on it. This naturally kept it quite wet or jellyfied even after some considerable time drying. when i peeled the stickers off, the edges of the photoresist tore giving a rough edge... thus resulting in the uneven corrosion. looking at the depth, it is mostly equal though in places it seems to of lagged behind a little. I suspect due to the adhesive left behind from the vinyl sticker giving temporary protecting before it was dissolved.

Next time i intend to use a sharpie marker pen and colour in around the stickers, to give a nice sharp line. I think that will cure it.

Once i have corroded down to 1mm i may enamel the edges of the corroded section giving the etching a more prominent 3D look. again, trial and error will come in here i guess.

So not great at the moment... but this could be great with decorating pens turned from copper alloys.

Will start playing with stainless once ive got this to a condition im happy with.

 

[BRobbins629]

I've also had limited success with etching copper and brass. I did mine with galvanic etching in a copper sulfate solution. Used an old computer power supply which worked well. Problem was I never did find a good resist that withstood the time necessary to get a good etch. Tried special paper designed for it, Rustoleum paint, fingernail polish, paint markers, and an industrial adhesive film. I did get an etch, but usually had a poorly defined border and unwanted areas where the resist didn't hold. If you ever find a really good resist, let us know. I had better luck carving the metal away on my CNC.

 

[BradG]

Thanks for your sharing your findings Bruce. Im curious if you ever experimented with different etchants? just as i wonder if it were the same solution, perhaps something a little weaker, albeit would have increased the etch time, may not have been so aggressive on the masking

 

[mredburn]

you might consider putting your stickers on, warming it just enough to melt wax and coat it. You could use the sharpie around the stickers as well. would a past wax work as a resist?

 

[BradG]

Mike
I imagine it would, and wax is certainly worth trying too.

As i have a UV exposure unit i think i will pick up a sheet or two of dry photoresist film, and try to roll it onto the brass, and iron it oppose to putting it through a laminator

 

[mredburn]

We used to use wax when making brass, copper and silver plates. In most cases the brass and copper etched plates were used for pressing the pattern into annealed silver plate using a rolling mill. However sometimes they were used as the finished product as well.

 

[BradG]

Thanks Mike

Il try the wax this evening and post the results

 

[BradG]

Etching experiment #2 .

This time using wax as a mask (as suggested by Mike) a much crisper outline was acheived, and this time with temperarture raised to 28'C and etched for one hour with again a concentration of 70/30 Ferric chloride, a deeper etch was yielded at 0.2mm. Wax is an effective mask. giving fantastic outlines, it is however troublesome with small details such as the dots in the middle of letters tend to peel off with the vinyl stickers on small fonts.

I tried to mask these back in with a marker pen and as you can see the marker will give unpredictable results and though it may be effective for tyouching up it wont be effective as a mask alone. prehaps with a sharper nib maybe? but it won't be my mask of choice.

To make it easier on the eyes i have coloured the etched layer black and what may appear to be a rough edge of the outline, would actually be my painting skills which i am yet to perfect, such as my etching skills.

I have some dry photoresist film on the way from hong kong which is sensitive to UV exposure. this is the same material i use for manufacturing printed circuit boards and i can acheive some very sharp details it. test number 3 will be with this.

 

[Dalecamino]

Much better this time around Brad. For sure....Mike is NOT just another pretty face :biggrin:

 

[BradG]

Coming along Chuck.

Excited about receiving the dry photoresist.

Here is some more details on what im up to with this concept:

The concept design.
all black areas will be etched and then either coloured or filled. possibly with PR or aluminite. That will be a full set of experimentation altogether when i get to that stage. This should give metal cogs curling around the body of the pen