A pair of Airfix Hawks in 1/72. Finished.

[Fritag]

1 hour ago, Fritag said:

I'll try again with a tad hotter iron (wool setting) and a tad longer exposure (2:00)

Hmm.  That didn't work.

 

I diligently cleaned a new bit of brass sheet with wire wool and IPA and used the iron to back up the laminator and a longer UV exposure.

 

Both the exposed and unexposed resist washed off the brass after only 1 minute in the caustic solution:

 

 

I'm off out tonight so no more experimenting today.

 

On reflection I probably changed too many of the variables at once (e.g. maybe the UV exposure was now too long?).  Need to be a bit more systematic.

 

Tomorrow I'll go back and check that the resist and caustic soda I bought were the same as on Mark's list.

 

I'll also have a rethink and see if I'm making any schoolboy errors.

 

Could also try reducing the strength of the caustic mix.

 

Steve

 

 

Edited September 23, 2017 by Fritag

[giemme]

Thrilling stuff! I really hope you find your way through this, Steve (I'm afraid this will raise your fares for the service, though )

 

BTW, and OT, I read LOTR a few times (say 30), but always in Italian, so I had to google for that word. It is my strong intention to read it in the mother tongue though, so I now have one less word to worry about

 

Ciao

[Cheshiretaurus]

It could be that the dryfilm you have is slightly different than what I used. I'm reading up on some PCB making instructions of using sodium carbonate as a developer and sodium hydroxide as a stripper.  

 

Sodium carbonate is avaible on eBay not sure what strength solution to make maybe start with 1% 

[keefr22]

Chemistry was one of my favourite subjects at school, very nearly chose to study it at Uni....however this alchemy now somehow fills me with dread! Good luck with the next experiments Steve!

 

Keith

[Gene K]

20 hours ago, giemme said:

Thrilling stuff!

I'll say! As a muta dotard, I've been sheepishly in the dark about this alchemy, so I'm glad Steve is exposing me to new developments. In that regard, I've been glued to my computer chair, and can't resist constantly checking ... I 'm so nervous that I need some sodium bi-carbonate (that's not meant to be a caustic comment).  Steve has some brass spheroids as well as plates, and I hope he gets this all ironed out promptly so I can rest.

 

Gene K

[hendie]

Well, I've been thinking about this and the only thing I can come up with is.... it's the resist, or to be more precise, the resist is not bonding to the brass. Now someone just has to figure out why. (I'm following the mantra of my forum title here in case you were wondering)

 

Back over in the tutorial, Mark states (my emphasis in bold):

On 8/2/2013 at 7:58 AM, Cheshiretaurus said:

The resist is a negative resist so the bits that get exposed to UV cure and harden while the unexposed bits stay weak, the resist should be stored in the dark and away from sunlight. It should also be kept away from sunlight and bright lights while your work with it until it has been developed.

While back on page 94,  our illustrious explorer writes:

On 9/20/2017 at 4:03 PM, Fritag said:

(3) The resist liberated temporarily from its black plastic light-proof security blanket.  Cor this is stressful..........

 

 

So, the questions I put to the witness m'lud...

 

At this time, was the resist opened in a situation where it could have been subjected to daylight even for brief periods?  Or bright lights? Daylights bulbs?

 

Is it possible that the resist sucked in some of those parma violets and partially developed itself?   Perhaps not enough to be visually noticeable, but just enough to prevent safe, secure, and proper adhesion to the brass substrate.  (or could it be an iffy batch of resist.  Much less likely I know but...)

 

 

 

That's all I got, sorry

 

 

 

[Fritag]

1 hour ago, Gene K said:

I'll say! As a muta dotard, I've been sheepishly in the dark about this alchemy, so I'm glad Steve is exposing me to new developments. In that regard, I've been glued to my computer chair, and can't resist constantly checking ... I 'm so nervous that I need some sodium bi-carbonate (that's not meant to be a caustic comment).  Steve has some brass spheroids as well as plates, and I hope he gets this all ironed out promptly so I can rest.

 

Awesome Gene.

 

22 hours ago, Cheshiretaurus said:

I'm reading up on some PCB making instructions of using sodium carbonate as a developer and sodium hydroxide as a stripper.

There's a Marlins just up the road from me in Harrogate so I opted in there to day and got some of the PCB photoresist developer that they sell.  It's Disodium Meatasilicate (apparently - I shan't pretend that this means a great deal to me at the mo' )

 

Anyways I tried another test with a 1 minute UV exposure - just using the laminator (no ironing) and a dunk in the Disodium Meatasilicate mix (7.5g of Disodium Meatasilicate to 75ml water) for an aggregate total of 2 minutes.

 

And it was rather more successful:

 

 

Lost some of the crispness of shape of several of the VGs.  But it is a wholesale improvement and I'll try again later backing up the laminator with an ironing.

 

A positive step forward or a blind alley?

 

 

 

 

 

[Cheshiretaurus]

Success 

 

I'll add that to the tutorial when I get chance. And the bonus is we now know how to strip the resist later. 

 

May I ask how much the developer was from Maplin?

 

CT 

[giemme]

Firstly, I agree with CT: success!

 

Secondly, I didn't know Gene was a poet;

that just sums up to his qualities

 

Ciao

[perdu]

That looks the thing Steve, meteathingywotsit, I mean what else could it have been?

 

 

I'm bustin' a gut to see how these come out

 

😱

[TheBaron]

Ditto on the air of tension here Steve. This hyar thread is dangerously close to becoming an HBO series in its grandeur.

House of Brass or summat of that ilk.

Keep it up mister - we're well gripped.

 

[hendie]

so it wasn't the Sun Gods having a little in-joke then.

 

Good to see you defeated the gremlins and got to the next stage.   As with t'others I am also on tenterhooks awaiting the outcome

 

[Fritag]

11 hours ago, hendie said:

so it wasn't the Sun Gods having a little in-joke then.

 

I don't think so.  Nothing I've read has suggested that the dry resist is so reactive to 'normal' light that you can't briefly take it out to cut off a piece etc.  But it's really quite cheap for a couple of meters at 15cm width (£2-£5 depending) and so I've ordered some more from a random different supplier to see if it reacts differently.

 

17 hours ago, Cheshiretaurus said:

Success 

 

I'll add that to the tutorial when I get chance. And the bonus is we now know how to strip the resist later. 

 

May I ask how much the developer was from Maplin?

Success-ish.  I'm still having problems at the developer stage.  The resist is at least adhering to the brass but I'm tending to lose definition at the edges - the resist is getting attacked/worn away randomly at the edges.  Not quite cracked it yet....

 

The Maplin developer was expensive compared with the materials from eBay - £9.99 for 250ml.  The recommended mix ratio is 10g/100ml.  I only got it because it had the merit of being instantly available.

 

BTW.  I tried again with the caustic soda (I looked back at CT's tutorial and the carton of caustic I have is exactly the same as CT's) but at a 2% rather than 5% solution and the results were better - but the resist UV exposed resit still softened and came away at the edges and in places.

 

11 hours ago, hendie said:

Good to see you defeated the gremlins and got to the next stage.   As with t'others I am also on tenterhooks awaiting the outcome

 

I advise against holding your breath 

 

My problem is getting the resist to adhere well enough to the brass and so the next things I'm going to work on are:

 

(1) putting more effort into cleaning the brass.  I'm gonna try roughening the surface slightly more (in case the wire wool is polishing it a bit) and cleaning it with acetone.  I may have been a bit blasé about this aspect.

 

(2) trying the different supply of dry resist.

 

Daft as it may sound - I'm thoroughly enjoying this despite the setbacks.  It's mojo-restoring in its own way.

 

 

 

 

Edited September 25, 2017 by Fritag

[giemme]

6 minutes ago, Fritag said:

Daft as it may sound - I'm thoroughly enjoying this despite the setbacks.  It's mojo-restoring in its own way.

Totally understandable (my favorite part in my real time job, BTW: trial and error to develop new machines/solutions  )

 

Ciao

[CedB]

Well done for persevering Steve - and thanks for sharing the experience

Good to hear you're trying to make Telford, it'll be great to meet up.

[Fritag]

10 hours ago, Fritag said:

I advise against holding your breath 

 

Ok - you can let your breath out now - but only a little, as you there'll no doubt be more setbacks at the etching stage  

 

I seem to have arrived at a workable solution to get through the troublesome (to me) development stage.

 

I think perhaps my main problem was inadequately preparing the brass .

 

On this test piece I used a square of 320 grit Tamiya sanding sponge (pictured here upside down under the brass) to prepare the brass sheet (sanding in 4 directions) and then wiped it with acetone.

 

I applied the dry resist using CT's water drop method.

 

Then ran it through the laminator 4 times.

 

Then gave it a total of 1min 15 secs in the Maplin developer mix (Disodium Metasilicate) - taking it out to inspect and run under the cold tap after 30 seconds and 1 minute.

 

And I reckon if I'd done both front and back resists it would have been worth a dunk in the etching solution!

 

 

Definitely better than my best effort from Saturday:

 

 

Phew......

 

I've run out of modelling time for tonight now 

 

But with luck tomorrow night I can move boldy forwards until I bang my head against the next brick wall!!!!

 

9 hours ago, CedB said:

Well done for persevering Steve

 

I will "endeavour to persevere" Ced.........but I won't declare war on the Union 

 

Steve

Edited September 25, 2017 by Fritag

[keefr22]

Good work Steve!

 

Keith

[giemme]

24 minutes ago, keefr22 said:

Good work Steve!

 

Keith

Amen to that!

 

Now that you've found a way, I'm looking forward to the little VGs being placed with great anticipation

 

Ciao 

[CedB]

Ditto, likewise.

That last lot looks worth a dunk... hopefully?

Looking forward to the next run

[Tomoshenko]

Ditto dittoed. Fine work Steve. An excellent tutorial.

[Fritag]

 

On 25/09/2017 at 8:53 PM, Tomoshenko said:

Fine work Steve. An excellent tutorial.

 

Hmm.  Trying to follow CT's excellent tutorial to be pedantic about it........

 

On 25/09/2017 at 8:41 PM, CedB said:

Looking forward to the next run

 

Next run done Ced.  And...

 

We have some etched VGs......Bloomin 'eck....

 

I think the key to success in the developing stage is, as I'd come to believe, proper prep of the brass sheet.

 

I prepped both sides of two bits of brass sheet, one for a test shot of 1.5mm VGs and one for some 1mm VGs, using the 320 grit Tamiya sanding sponge and acetone and got through the developer stage nice and neatly.  Here's a piccie of the two sides after developing:

 

Front.  Note the mounting stub connects to the carrier frame.

 

 

Back.  Note the gap between the mounting stubs and carrier frame as per CT's methodology for etching the brass to half thickness for easy detachment.

 

 

Before etching I followed a tip I found during general internet browsing - and popped the developed sheets back under the UV light for 1 minute each side to harden the resist that bit more.

 

The etching solution I used was a ready-mix Ferric Chloride solution (one of the etchants recommended by CT) I picked up at Maplins when I took an emergency detour in the Harrogate store on Sunday for the different developer.  A bit of a whim purchase and rather unnecessary seeing as I already have some Sodium Persulfate powder I got from eBay months ago.  But hey - I was feeling vulnerable and needed a comfort blanket........

 

Anyways.  I diluted the ready-mix 2 parts ferric chloride to 1 part water - just to slow the process down a bit, and dunked the 1.5mm VGs.

 

At which point I remembered I'd forgotten to get any plastic tweezers!  So has to improvise some tweezers using spare wooden coffee stirrers.............

 

To my relieved surprise - after about 45 minutes or so (punctuated by lots of impatient lifting and looking) I had this:

 

 

Which after stripping away the resist with a dip for a minute or so in a caustic soda mix left this:

 

 

I lost a couple of VGs being a bit clumsy running the etch under the tap to wash away the softened resist  So at least I know that CT's method for reducing the brass thickness at the attachment point works!

 

To say I'm pleased would probably be an understatement 

 

Not all of the VGs are quite perfect in shape - I was a bit impatient in ending the etching process and I think another few minutes would have crisped up the edges on the recalcitrant ones - but there are enough good ones to use if I wanted to (and in any event I think a few gentle swipes with the Tamiya diamond file on the imperfect ones would do the trick). 

 

I'll etch the 1mm VGs after work  later today.

 

If they come out all right I'll have to choose which ones look better tested fitted to the spare wing- the more scale correct 1mm ones - or the slightly overscale 1.5mm ones -  and then I'll put all this practice to use and make a set for fitting to the hawks

 

Phew.......

 

Thanks Mark (@Cheshiretaurus).  I would neither have attempted it nor got anywhere near success without your excellent tutorial 

 

 

 

 

Edited September 27, 2017 by Fritag

[abat]

Well done. They look tremendous. 

[giemme]

    He made it!    

 

Great going, Steve!

 

Now I can start preparing my PE wish list ...      

 

Ciao

[keefr22]

Fantastic stuff Steve!! 

 

Keith

[perdu]

Brilliant

 

Well done Steve, best news yet this week

 

They do look fine and let's face it we always make more than we need don't we

 

So you'll be preparing another dozen sheets of the little blighters

Fritagetch is on the road!

 

Yeehaw!

 

☺