Checking the pad with acid
Thread Starter
Racer
Joined: Jan 2010
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From: Rochester ny
Checking the pad with acid
I have seen a lot of references about how to check if a pad was restamped by using acid. I spent 45 minutes searching, but havent found a post about how to do it. So, how do you do it? What kind of acid do you use? If you are careful (maybe use a q-tip?) do you think a seller would allow you to do this?
Thanks.
Mike
Thanks.
Mike
Le Mans Master
Joined: Mar 2009
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From: Cold Harbor, VA
Uh, ummm, no.....
I have seen a lot of references about how to check if a pad was restamped by using acid. I spent 45 minutes searching, but havent found a post about how to do it. So, how do you do it? What kind of acid do you use? If you are careful (maybe use a q-tip?) do you think a seller would allow you to do this?
Thanks.
Mike
Thanks.
Mike
Burning Brakes
Joined: Jun 2000
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From a Model T forum:
"Years ago, I was a Deputy Sheriff. We used a battery charger clamped to a cotton ball, soaked in sulfuric acid to raze serial numbers on stollen guns and cars. The molocules were compressed by the original stamp, and the old number appears as dark impressions."
"Years ago, I was a Deputy Sheriff. We used a battery charger clamped to a cotton ball, soaked in sulfuric acid to raze serial numbers on stollen guns and cars. The molocules were compressed by the original stamp, and the old number appears as dark impressions."
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OK, so let's say a (bare) block is on an engine stand and at sometime in its past, the block got surfaced. What would be the acid process for trying to raise the numbers? I have a Jan 67 SB that's been surfaced and I'd like to know what it was. I really want to know, because it is a somewhat rare BIG JOURNAL 67 (Jan) block.
Tom Parsons
Tom Parsons
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Tom , I have heard of various techniques to raise the outline of the compressed molecules and thus read the numbers, talk to any auto theft cop, they don't use the acid thing any more, they have some kind of infrared hand held gun thing that looks like its out of Startrek or N.C.I. That's why thieves routinely arc weld over numbers instead of grinding, as that destroys the molecular pattern in the metal. I think it will depend on how much material was removed on your block. Definitely worth a try.
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Thread Starter
Racer
Joined: Jan 2010
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From: Rochester ny
I hope some others chime in. What good is the test if a seller wont allow it? (unless you already own it and just want to be sure like Tom.) Ive read all the posts on restamped numbers and nobody can agree on one if their life depended on it. This whole matching numbers thing seems like BS unless there is some consensus on how to tell for sure...or at least 90%...75%...51% sure.
I dont believe its a one time thing. The acid wouldnt destroy the numbers, it would just reveal previously stamped numbers.
I dont believe its a one time thing. The acid wouldnt destroy the numbers, it would just reveal previously stamped numbers.
Thread Starter
Racer
Joined: Jan 2010
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From: Rochester ny
Drifting
Joined: Nov 2007
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From: columbus ohio
i have seen the test done when i was a po at the crime lab. i do not know
what it would do to the metal with a legit stamp on it. i would try the
other side of the block for a test before the vin side. personally i would
make someone pay me before the test. jim
tom, i would try it on the block what do you have to loose. call your
local law enforcement and ask for their crime lab. i am sure they will
tell you how to do it, or it may be on google. jim
what it would do to the metal with a legit stamp on it. i would try the
other side of the block for a test before the vin side. personally i would
make someone pay me before the test. jim
tom, i would try it on the block what do you have to loose. call your
local law enforcement and ask for their crime lab. i am sure they will
tell you how to do it, or it may be on google. jim
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From: Bowling Green, Kentucky
Larry
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From: Bandera Texas
i have seen the test done when i was a po at the crime lab. i do not know
what it would do to the metal with a legit stamp on it. i would try the
other side of the block for a test before the vin side. personally i would
make someone pay me before the test. jim
tom, i would try it on the block what do you have to loose. call your
local law enforcement and ask for their crime lab. i am sure they will
tell you how to do it, or it may be on google. jim
what it would do to the metal with a legit stamp on it. i would try the
other side of the block for a test before the vin side. personally i would
make someone pay me before the test. jim
tom, i would try it on the block what do you have to loose. call your
local law enforcement and ask for their crime lab. i am sure they will
tell you how to do it, or it may be on google. jim
Three weeks later a friend, who was also a CHP, stopped by one Saturady morning and while having coffee noted the vin number on the engine and with my friends permission, ran the number. Yep......you guessed it. Engine was stolen in 1969. They wanted to confiscate it, but when the old owner and car were not found in any modern records today, the let my friend keep it.
'BIG BROTHER' is watching.
Why don't you just post the photo here of the engine pad? There are a lot of very knowledgeable people on the forum.
Al Grenning is a great guy, and for his $300 fee you will get a letter of 'authencity' certifying the engine stamp. That may apply however to a whole car and trim tag, I am not sure.
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Careful here. Two years ago a friend bought a nice 67 427/390 engine at a swap meet. The engine came from a Corvette and had the old vin number still on it. That is why he wanted it, as he had a nice 67 with a replacement 69 Camaro 396 block and this swap meet engine was 85 or so vin numbers away from his vin and was the best he could find for the car.
Three weeks later a friend, who was also a CHP, stopped by one Saturady morning and while having coffee noted the vin number on the engine and with my friends permission, ran the number. Yep......you guessed it. Engine was stolen in 1969. They wanted to confiscate it, but when the old owner and car were not found in any modern records today, the let my friend keep it.
'BIG BROTHER' is watching.
Why don't you just post the photo here of the engine pad? There are a lot of very knowledgeable people on the forum.
Al Grenning is a great guy, and for his $300 fee you will get a letter of 'authencity' certifying the engine stamp. That may apply however to a whole car and trim tag, I am not sure.
Three weeks later a friend, who was also a CHP, stopped by one Saturady morning and while having coffee noted the vin number on the engine and with my friends permission, ran the number. Yep......you guessed it. Engine was stolen in 1969. They wanted to confiscate it, but when the old owner and car were not found in any modern records today, the let my friend keep it.
'BIG BROTHER' is watching.
Why don't you just post the photo here of the engine pad? There are a lot of very knowledgeable people on the forum.
Al Grenning is a great guy, and for his $300 fee you will get a letter of 'authencity' certifying the engine stamp. That may apply however to a whole car and trim tag, I am not sure.
I DO NOT want to ask anyone in the law enforcement arena.
I have this Jan 67 (327 or 350) bare block on a stand in the shop and it has clearly been surfaced in the past, thus, all the numbers are gone. It was given to me. A family across the street pulled it from their son's 69 pickup because it was using lots of oil and replaced it with a 350.
The block is also bored .040, but has NO DETECTABLE ridge at the top of the cylinders.
This is one of those very rare SBs for a LARGE journal crank, but has the REAR HOLE for a road draft tube/PCV valve adapter. I want to build this into a 383 and use NO HOLE valve covers to produce an early SB appearance.
I would just like to know if anyone here knows how to bring out the numbers that WERE on the stamp pad-----------------WITHOUT asking a law inforcement official about how to do it. It can certainly never be traced since it's been surfaced, but I just do not want to attract any undue attention from big brother!
Tom Parsons
Racer
Joined: Mar 2008
Posts: 338
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From: Mesa Az
EXACTLY!!!
I DO NOT want to ask anyone in the law enforcement arena.
I have this Jan 67 (327 or 350) bare block on a stand in the shop and it has clearly been surfaced in the past, thus, all the numbers are gone. It was given to me. A family across the street pulled it from their son's 69 pickup because it was using lots of oil and replaced it with a 350.
The block is also bored .040, but has NO DETECTABLE ridge at the top of the cylinders.
This is one of those very rare SBs for a LARGE journal crank, but has the REAR HOLE for a road draft tube/PCV valve adapter. I want to build this into a 383 and use NO HOLE valve covers to produce an early SB appearance.
I would just like to know if anyone here knows how to bring out the numbers that WERE on the stamp pad-----------------WITHOUT asking a law inforcement official about how to do it. It can certainly never be traced since it's been surfaced, but I just do not want to attract any undue attention from big brother!
Tom Parsons
I DO NOT want to ask anyone in the law enforcement arena.
I have this Jan 67 (327 or 350) bare block on a stand in the shop and it has clearly been surfaced in the past, thus, all the numbers are gone. It was given to me. A family across the street pulled it from their son's 69 pickup because it was using lots of oil and replaced it with a 350.
The block is also bored .040, but has NO DETECTABLE ridge at the top of the cylinders.
This is one of those very rare SBs for a LARGE journal crank, but has the REAR HOLE for a road draft tube/PCV valve adapter. I want to build this into a 383 and use NO HOLE valve covers to produce an early SB appearance.
I would just like to know if anyone here knows how to bring out the numbers that WERE on the stamp pad-----------------WITHOUT asking a law inforcement official about how to do it. It can certainly never be traced since it's been surfaced, but I just do not want to attract any undue attention from big brother!
Tom Parsons
Burning Brakes
Joined: Mar 2005
Posts: 1,231
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From: Ontario
Al Grenning
Careful here. Two years ago a friend bought a nice 67 427/390 engine at a swap meet. The engine came from a Corvette and had the old vin number still on it. That is why he wanted it, as he had a nice 67 with a replacement 69 Camaro 396 block and this swap meet engine was 85 or so vin numbers away from his vin and was the best he could find for the car.
watching.
Why don't you just post the photo here of the engine pad? There are a lot of very knowledgeable people on the forum.
Al Grenning is a great guy, and for his $300 fee you will get a letter of 'authencity' certifying the engine stamp. That may apply however to a whole car and trim tag, I am not sure.
watching.
Why don't you just post the photo here of the engine pad? There are a lot of very knowledgeable people on the forum.
Al Grenning is a great guy, and for his $300 fee you will get a letter of 'authencity' certifying the engine stamp. That may apply however to a whole car and trim tag, I am not sure.
I don't think you will get anything in writing from Al for $ 300.00 You will get his opinion for a fair price .
Bill Purdy
Racer
Joined: Mar 2008
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From: Mesa Az
Here's the link to the Camaro Research Group article on the process. I finally found it.
http://www.camaros.org/public/acidetch.txt
http://www.camaros.org/public/acidetch.txt
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Here's the link to the Camaro Research Group article on the process. I finally found it.
http://www.camaros.org/public/acidetch.txt
http://www.camaros.org/public/acidetch.txt
I'm going to give it a try and see what happens.
Tom Parsons
ACID ETCHING TO RECOVER ID STAMPS
Acid Etching to Recover ID Stamps Camaro Research Group16 Apr 2000.
If you use this procedure, please post a note on the CRG Forum with your impressions and results. Please heed the safety warnings and do not attempt this if you are inexperienced in handling hazardous materials.
I tried the acid etch, it looks like you can make out the number T0419JL.
The T04 L for certain the 19J are faint. Thanks for the tip on the acid etch.
Steve brewing1@home.com
The technical standard for metal etching is covered by ASTM
(http://www.astm.org/) E340, Standard Test Method for Macro etching Metals and Alloys. The ASTM standard contains background and details not included in this CRG draft. We strongly encourage anyone considering metal etching to obtain a copy of this either from the website (for a fee) or from your local library in Volume 3.01 of the ASTM Book of Standards.
THE PROCEDURE INVOLVES USE OF ACID, AND THERE ARE OBVIOUS SAFETY ISSUES ASSOCIATED WITH SUCH MATERIALS. USE SAFETY GLASSES AND ACID-RESISTANT GLOVES, READ THE SAFETY PRECAUTIONS ON THE CONTAINERS. IF DILUTING - ADD ACID TO SOLVENT RATHER THAN SOLVENT TO ACID, BECAREFUL OF FUMES, DO THIS IN A VENTILATED AREA, ETC.
The theory, for those interested, is that the cold-work of the stamping process changes the metal microstructure locally around the imprint, sufficiently so that there is a resulting difference in resistance (increase or decrease) to acid attack in the portion that has been
cold-worked. If the original stamp is removed, the material underneath retains this change in microstructure, which is not visible to the naked eye (until being revealed through etching). There is a limit to how much material can be removed during the decking process before etching will not reveal the original stamp. Obviously the deeper the current surface is below the original surface the less distinct any characters will be.
For illustration, here are the approximate steps for cast iron:
1) Prepare or purchase etching solution. There are numerous types of etching solutions. The "general purpose" solution in the standard for iron and steel is a 50/50 mix of concentrated hydrochloric acid and water. An easily obtainable close approximation of this is swimming pool muriatic acid, available from swimming pool and home improvement stores, usually already in a diluted form. (Note: a 160F-180F solution is suggested in the ASTM standard test method, but we strongly recommend avoiding use of a heated acid solution in a hobbyist garage. A room-temperature solution will work - but will take little longer.)
2) Remove all grease, dirt, and paint from area to be etched.
3) Mask off portions of the casting that you don't want etched. You don't want the etching solution washing down your cylinder bores!
4) Clean the pad with solvent and/or cleaning solution. "Any grease, oil, or other residue will produce uneven attack."
5) Saturate a cotton ball held in tongs with the etching solution, uniformly swabbing the area of interest. Wait for the "structure to be developed" (characters to appear). Since the estimate development time is 15-30 minutes you may have to repeat the swabbing periodically to keep the surface uniformly wet with etchant. When the characters become visible or it becomes obvious that they won't, you can stop.
6) Rinse the casting with hot water to remove the etchant.
7) If necessary, "de ****" the surface by vigorous scrubbing with a vegetable fiber brush.
8) Blow the casting dry with compressed air.
Pro
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From: WEST MILFORD NEW JERSEY
Etching acid
If you go to the local coin shop they sell a little bottle of acid for raising the numbers and letters on worn coins. I have used it on old buffalo nickels and mercury dimes and it worked .Give it a try. Good luck,Wes