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ACID ETCHING WITH POSITIV 20 AND NEGATIVE by Marietjie Thorburn

***ETCH THE LOGO ON THE BLADE OF A FIXED BLADE KNIFE BEFORE YOU PUT THE BOLSTER ON – YOU MIGHT HAVE TO RE-DO THE ETCHING AND IT WILL NOT BE POSSIBLE TO GET THE BLADE FINISH NEAT AND CRISP IF THE BOLSTER is ON. The logo will have to be removed by a belt grinder – so back to 320# belt, re-polish the hollow, the satin and then the ricasso. Rather be safe than sorry.

*** ETCH THE LOGO ON THE BLADE OF A FOLDING KNIFE BEFORE YOU DO THE ASSEMBLING (IF POSSIBLE) BUT ALWAYS BEFORE YOU FIT THE THUMB STUD.

WHAT TO USE

ITEM WHERE AVAILABLE

Thinners and Acetone Hardware shop / Supermarket

Tissue paper (toilet roll) Supermarket

POSITIV 20 / POSITIV RESIST Marietjie Thorburn , Knife Machines and Tools (KMT) or Electronic Shops

Masking tape

High Temperature 120º

Marietjie Thorburn, Knife Machines and Tools (KMT) Hardware shop / Supermarket

Wooden Pegs - modified to hold negative on blade

Supermarket

UV light box or sun light SEE ATTACHED DRAWING – I PREFER THE SUN LIGHT BUT UNFORTUNATELY THE SUN DOESN’T

ALWAYS SHINE

Brown Dropper Bottles (Qty 2) Chemist

Ferric Chloride Saturated solution – crystals at KMT

Caustic soda (flakes)/Bytsoda (in Afrikaans – nie Wassoda nie)

Caustic soda solution

Chemist / Supermarket

Recipe on Positiv 20 can – also see NOTE

Negative Knife Machines and Tools (KMT) or

Future Pre-press – 650 Windsor street Garsfontein

Karin Nolan karin@futuregroup.co.za

012 – 998 1642 or 012 998 5258

Liquid Gun Blue Knife Machines and Tools (KMT) or Gun shop

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NOTE

Negative - Knife Machines and Tools (KMT) or your local printer might also be

able to help. Design your logo in black and white - they will know what to do – just give them specific sizes e.g. 12 mm or 15 mm high. ONLY BLACK

AND WHITE (NO GREY OR SHADOWS).

NOTE

Caustic soda solution - 7g on 1 liter of water (level teaspoon). Keep solution in brown glass bottle as it is light sensitive.

METHOD

NOTE

Always remember: do not work in direct sunlight. If ever you have to stop the process - place the knife in a dark cupboard or cover with a soft dark cloth. The Positive 20 is light sensitive and it will loose its effectiveness within a few seconds.

NOTE

Etch logo on the LH side (presentation side) of the blade unless your client is left handed then the presentation side will be the right hand side of the knife. The logo must be close to the bolster and as high as possible. Remember your logo is an advertisement so you want it to stay on the knife.

NOTE

Work in a clean and dust free area.

(1) CLEANING OF THE BLADE IS EXTREMELY IMPORTANT. The blade must be absolutely oil and buffing soap free. Some buffing soaps may require you to wash it thoroughly using sunlight liquid. We use Unipol so we clean it with tissue paper and thinners (rub it well) and then with acetone (rub it extremely well to remove the thinners). A Mirror finish on the blade makes it more difficult to etch. Cleaning is then even more important. Spray the Positiv 20 and rub off immediately with a tissue then re- spray the Positiv 20 without cleaning the blade again.

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(2) Mask the bolster and handle with paper. Spray positiv 20 holding it 150 mm to 200 mm away. The film must be even and not

running. If you have sprayed too much and it runs on the blade you might have to expose it to the UV light for longer and leave the caustic soda on the blade for longer during the developing process.

(3) Leave to dry overnight or blow dry for 15 min. Allow to cool down

completely before continuing.

NOTE

The cooling is important as heat activates caustic soda and it might “eat” through the layer quickly. (4) Cut the negative to the correct size and mask using masking tape – cut to size again.

(5) Keep ready:

• Tissue paper. • Caustic soda solution in brown dropper bottle. • Ferric Chloride (FC) solution in brown dropper bottle. • Wooden pegs – modified to hold negative close to blade even in

small corners.

(6) Place the negative on the blade - make sure that it is straight.

(7) Clamp negative using wooden

pegs - negative must be flat on the blade.

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(8) Expose the blade to the light in the light box – experiment with your specific light bulb, as you will have to find the perfect time for it. For example: if using an OSRAM 160 W HWL ® (MBTF) B22d 240 V mercury tungsten blended lamp you have to expose the blade to the light for 5 min. Using another bulb might only require 25-30 sec. Remove one wooden peg to do the colour test (see 9)

OR Expose to direct sunlight for 25 sec to 30 sec. Hold very still and avoid shadows. Do the thumb test to see if you have to expose it a few seconds longer ( see 9)

(9) Positiv 20 changes colour (green ››› blue) when exposed to light. This

is always a good indication that your blade has been exposed to the UV light for long enough. Do not remove the negative unless you are sure that the change has taken place. You will never be able to put the negative back on and you will have difficulty developing the image. If the difference in colour is not clear - expose to the UV light again - remember to time this so that you will know how long to expose it in

the future.

(10) Remove the negative. Store it in a safe place as you can re-use it and you don’t want it to get scratched.

(11) Place a drop of caustic soda on the blade. Take care not to touch the

blade with the dropper as the Positive 20 layer can easily be damaged. Keep a tissue ready and as soon as the image has been fully developed dap dry. Never rub as the tissue might have a dust particle that can scratch the layer. You can be sure that it has been fully developed if the blue layer has been completely removed. NO GRAY

SHADOWS MUST BE

VISIBLE ON THE IMAGE. The image must be shiny - if not place another drop on the image and dap dry with a tissue after a while.

NOTE

It is a good idea to test a freshly mixed Caustic soda solution before you use it the first time. Test it on the tip of the blade if it develops to quick add a bit of water and if it takes too long add Caustic soda flakes.

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NOTE

ALWAYS:- DAP THE CAUSTIC SODA OFF THE BLADE IMMEDIATELY AFTER

YOU’VE APPLIED IT – DOING THIS YOU’LL BE ABLE TO DETERMINE THE SPEED AT WHICH THE IMAGE DEVELOPE. A FEW FACTORS DETERMINE THIS LIKE:

• EXPOSURE TIME

• LIGHT OR SUN LIGHT

• THICKNESS OF THE POSITIV 20 LAYER

• DRYNESS OF THE POSITIV 20 LAYER – 1 HOUR/ 1 DAY / 1 WEEK

(12) Mask the image using a permanent marker. It is like building a dam wall around the image to keep the ferric chloride in. Anything suspicious can also be covered with the permanent marker.

(13) Drop a large drop of ferric chloride inside the masked area (dam wall). Make sure that the image is completely covered as the FC tend to move away from the edges. Leave for about 2 min. You will be able to see the reaction - the image will loose its shine and turns darker. When the etching looks even coloured - suck the FC back into the dropper bottle. Leave just a little bit on the blade and avoid touching the Positiv 20 layer with the tip of the dropper. It is an oxidization process – use the tissue or ear bud containing a little Ferric chloride to dap the etching. The oxygen and the FC will react quickly and the image will turn darker. When the image is uneven in colour or still shiny you will have to go back to step 11. Repeat the process as it means that the image hasn’t been completely developed.

**Remember to re-do the permanent marker as the caustic soda might

damage the layer of ink.

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(14) To get an even darker etch you can also put a little liquid gun blue on an ear bud and dap – while there is still a bit of Ferric Chloride on the blade. This works well on steels like 440B that’s really difficult to etch.

(15) When happy with the outcome place a large drop of caustic soda on the image and rub well. Repeat two or three times to completely remove all the ferric chloride.

(16) Finally clean the blade using

acetone on a tissue.

Remember the saying:

W hen you don’t have tim e to do it right… … … … … W hen w ill you have tim e to do it over????

Please take your time with the process. Rather be safe than sorry! Marietjie ThorburnMarietjie ThorburnMarietjie ThorburnMarietjie Thorburn

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STRYKYSTER ( HAAL DIE KREUKELS / PLOOIE UIT! ) - TROUBLESHOOT:

� POSITIV 20 TREK WEG EN MAAK DRUPPELS:- - MAAK SKOON MET TERPENTYN OF SUNLIGHT LIQUID ( GEWOONLIK SPIEëLAFWERKING

(MIRROR FINISH)– BUFF) - GEBRUIK ‘N STUKKIE SNEESPAPIER EN SMEER DIE POSITIV 20 OOR DIE LEM – MOENIE

SKOON MAAK NIE – SPUIT DAN WEER

� POSITIV 20 RAAK MELKERIG: – - TE VEEL VOG IN DIE LUG – MAAK DIE LEM SKOON EN DAN WARM VOOR JY WEER SPUIT.

WERK BY ‘N VERWARMER WAT DIE LUG UITDROOG.

� WIL NIE ONTWIKKEL NIE:- - BYTSODA KAN TE FLOU WEES - OF VERSLAAN HET. (LIG EN LUG SENSITIEF) - POSITIV 20 HET TE DROOG GERAAK – LANGER AS ‘N WEEK GELê - LAAG POSITIV 20 TE DIK - ONTWIKKEL STADIGER ( DIKKER LAE MOET LANGER BELIG

WORD OM ONTWIKKELING TE VERGEMAKLIK).

� BYTSODA VREET DADELIK DEUR DIE LAAG -- BLINK KOL OF PIT MERKE - BYTSODA TE STERK - POSITIV 20 NOG NIE DROOG NIE - LEM NOG WARM NA DIE DROOGMAAKPROSES MET HAARDROEëR OF

VERWARMER.( HITTE AKTIVEER BYTSODA)

� FERRIC CHLORIED TREK WEG – DRUPPEL:- - DE – MAGNITISEER DIE LEM - HOU LEM WATERPAS (LEVEL) DEUR WASGOEDPENNETJIE ONDER DIE PUNT VAN

DIE LEM IN TE WIG.

� ETS NIE EGALIG NIE – BLINK STUKKIES BLY:- - ONTWIKKELING ONVOLDOENDE – HERHAAL VANAF STAP 11

� LOGO IS NIE HELDER (CRISP) NIE:-

- SWAK NEGATIEF – “DOT-MATRIX” ( KOLLETJIES) – ETS SO GOED AS WAT JOU NEGATIEF IS. - NEGATIEF WAS NIE PLAT TEEN DIE LEM NIE - GEBRUIK WASGOED- PENNETJIES WAT VIR DIE DOEL AANGEPAS IS.

� ETS IS NIE SWART NIE:-

- PARTY SOORTE STAAL ETS MOEILIKER – VERBETER MET LIQUID GUN BLUE – SIEN STAP 14 VAN AANTEKENINGE. - IN KOUE, NAT EN WINTER TYE KAN JY DIE FERRIC CHLORIED BIETJIE WARM MAAK (SIT BOTTELTJIE IN BAKKIE WARM WATER) - HITTE AKTIVEER DIE

FERRIC CHLORIED.

� ETS ALLERHANDE MERKIES – SELFS KRING OM DIE LOGO:- - NEGATIEF GEKRAP? - BêRE NEGATIEWE WEG VAN STOF – IN BOEK - STOFMERKIES IN POSITIV 20 LAGIE – MAAK MET PERMANENTE PEN TOE - GEBRUIK ‘N STERKER BRIL AS JY DIT NIE VOOR DIE TYD KAN SIEN NIE - FERRIC CHLORIED HET NIE ‘N BRIL NODIG NIE!! - PITMERKIES ORAL WAAR BYTSODA WAS – MAAK SEKER DIE POSITIV 20 LAGIE IS NOG BLINK NADAT DIE BYTSODA OP WAS – INDIEN DIT ENIGSINS VAAL

LYK VERAL OP RAND VAN DIE BYTSODA DRUPPEL – MASKEER MET PERMANENTE PEN. BYTSODA OPLOSSING TE LANK

GELOS OF DALK TE STERK.

� ETS GLAD NIE :- - HET LEM NET MET THINNERS SKOON GEMAAK – THINNERS LAAT ‘N OLIELAGIE OP DIE LEM WAT VERHOED DAT DIE FERRIC CHLORIED BY DIE STAAL KAN UITKOM. GEBRUIK ALTYD ASETOON AS LAASTE STAP IN SKOONMAAKPROSES. - VERKEERDE STAAL - GEWONE VLEKVRYESTAAL ETS NIE MET FERRIC CHLORIED

NIE - MESSTAAL MOET HITTEBEHANDEL WORD VOORDAT DIT GOED ETS.

----Fluit-fluit my storie is uit----

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