# Casting Vintage Stamps in Acrylic using Silmar 41



## Schroedc (Sep 5, 2016)

This process was worked out using Silmar 41 and older US stamps made prior to the mid/late 1960's. Casting newer self adhesive stamps have a few other hurdles with the adhesive and later stamps that aren't printed using engraved plates used different inks that can create issues. The best way to determine if the stamps are a good candidate for this process is to feel them and feel if they are textured similar to US Currency.

Step 1- Select the stamps you're going to use. I prefer unused stamps as they are generally in better condition but used stamps do work although the cancellation marks can occasionally bleed during the casting process, Also, used stamps sometimes were removed leaving a layer of paper on the envelope so they are thinner and harder to work with. These are for a run of 18 pens I'm going to do for the shop. I like to pick subjects that are visually pleasing, or relate to a show I'm doing or a segment of my customer base (Around here Boy Scouts, FFA, Military, and Wildlife sell quite well)





Step 2- Next the stamps get a bath, I lay them face down on my hand, under COLD running water (Warm to hot can cause the paper to fall apart) and gently rub to wash off the adhesive. I'll also rinse the top side to remove any soil but be gentle. these are 50+ years old. Removing the gum helps with better adhesion when placing on the tube and also if left can bleed through to the front during casting causing stains.





I'll then blot them a bit with a paper towel and lay them out on a clean towel to dry. They might curl a bit but that's OK, you'll be able to fix that when mounting.





Step 3- Tube preparation. You'll want to work with white painted tubes for this (I'll explain later why brass or black is a bad idea) I'm making Mesa style pens using the 27/64ths tube and I prefer to just buy pre painted tubes from my supplier as most of them are a heat cured finish or catalyzed enamel that won't create issues during casting. The ones I use from Woodturningz.com work out about 1.50 a tube or less depending on quantity and for the time I save and not having to paint myself it's worth it IMO.





Mount the tube on your lathe (You can do it totally by hand but if you have the centers why not do it the easy way) bring up to speed and using #0 or #1 steel wool or a grey Scotchbrite remove the gloss. This also makes sure any residue from the painting process or bags is removed.

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## Schroedc (Sep 5, 2016)

Ok, The stamps we washed earlier have had a couple hours to dry so now on to Step 4, Mounting the stamps on the tube.

I use Modge Podge for my adhesive, sets up fairly quick but not too quick. A fine synthetic bristle brush (I like a 1/2 inch brush, bought it in the painting supplies aisle at Hobby Lobby) Your prepared tube, and 2 stamps.

** A note here- I lay out my stamps at an angle, a bit of space at the edges to show the perforations. This is my personal preference. You can use more stamps, or smaller ones if you wish but I wouldn't overlap different colors much as I'll explain why when we cast them.

I brush on a light coat of glue and working quickly get it on the tube where I want it (You can slide them a bit to get exactly where you want if you're quick, wait too long as the glue sets up and you'll tear the stamp) If you got an even coat of glue the stamp should stick well and you can let go after 20-30 seconds or so. Try not to apply too much glue as it'll squoosh out the edges and get on your fingers and you can leave fingerprints on the stamp that'll show when cast and turned.



 



 



 

Then I take the second stamp, without glue put it where you want it and wrap it around the tube to get an idea of what overhangs. I use a razor blade to cut the stamp a hair over the edge for adjustment and error room (Don't worry, you'll trim this off later)



 



 

Then apply a light coat of glue with the brush, stick it where you want it and use the piece you cut off to do the other end (It looks like you use 3 stamps to do it this way but you only have to have two) If a corner doesn't want to stay down, apply a tiny bit of glue under the edge with your brush and hold for 30 seconds or so.



 

Now set your glued up tube somewhere for 24 hours to let the glue dry and make sure the stamp is completely dry. Then We'll do the fun part!

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## Schroedc (Sep 5, 2016)

Ok, Thanks to the magic of the internet it's been 24 hours 

Take a razor blade and trim the excess stamp off down to the end of the tube.



 

Then place in your mold, mix and pour your Silmar-41. The instructions call for 10 drops of catalyst per ounce but I've found that while you have a longer set time you get better results at 7-8 drops per ounce. I am not using a pressure pot. I place the mold on the table saw or router table and retract the blade/bit and turn it on. The vibration help to get any tiny bubbles to float to the top (Another reason for a bit less catalyst is more time for bubbles to float out) I'll usually vibrate it for 20 minutes or a hair more. After that the resin is starting to thicken and what you gots is what you gets.



 

Ok, now we come to the technical part about why this process is specific for older stamps, the white tube and all..

"Wait Colin, Aren't you going to seal the paper before casting?"

Here's the skinny, After trial and error, lots of error I found that you can seal the stamps with CA or a couple other products but the results weren't what I was happy with. If you have a pin hole in the sealer the resin will soak in causing the paper to turn somewhat translucent. You can also wreck the stamp if the sealer dissolves the inks and smears them all over. If you have a black or brass tube under the stamp it'll become dark whereas with a white tube it'll actually become brighter and more vibrant. This was also the reason for washing off the adhesive. Not only does it make them easier to glue onto the tube (Try it once without, It makes a mess) the original glue can dissolve in the resin and soak up through the paper causing brown stains. Here is the finished result after the resin cures overnight and turning and polishing. I've placed original stamps below them so you can see how the colors pop after casting. After I get some more done I'll assemble with the pens and off they go to my adoring fans 



 

Do let me know if you have any questions and I'll do my best to answer them. Also, if you've discovered methods that work and are willing to share please feel free to let all of us know.

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## ripjack13 (Sep 5, 2016)

Awesome!! Great posting Colin.

Reactions: Like 1 | Agree 2


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## DKMD (Sep 5, 2016)

That's an awesome tutorial! Thanks!

Reactions: Like 1


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## woodtickgreg (Sep 5, 2016)

Very cool and awesome looking.

Reactions: Thank You! 1


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## Wildthings (Sep 5, 2016)

What a great tut! Very well done and easy to follow! Much appreciated!

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## Sprung (Sep 5, 2016)

Very nicely done, Colin!  Thanks for the great tutorial! As you've mentioned previously, this is a realm of pen making that not many people are willing to share information on, which makes it difficult for anyone interesting in learning the process.

Reactions: Agree 1


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## Schroedc (Sep 5, 2016)

Sprung said:


> Very nicely done, Colin!  Thanks for the great tutorial! As you've mentioned previously, this is a realm of pen making that not many people are willing to share information on, which makes it difficult for anyone interesting in learning the process.



Well, there is one magic, super secret step I'm not telling you all........

Just kidding. Yep, I wanted to get into it and there was very little for quality, clear, easy to understand references out there so I combined the bit I could find with about 3 months of research and failures, learned what didn't work and even the failures will be applicable in other things I do down the road as they pointed me in new directions.

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## Schroedc (Sep 6, 2016)

So I thought I'd follow up with an add on for those who want to cast but are a bit put off by the cost of the silicone molds. I do have a couple I use for test runs or one/two pen orders. When I'm doing a run of any quantity I use a big bar mold I made out of HDPE. I get HDPE cutting boards form a local restaurant supply place and use rubber plugs from the hardware store that fit into the end of the tube (Once you know what size you want, go online and buy a bag of 50 or 100, It's way cheaper and then you have spares to lose). The HDPE cuts just fine on a table saw, you can make any size mold you want (I've made a few for 4 inch squares too) And you just cut the plugs so that when inserted in the tube it's a bit longer than the mold width and friction keep the tube in place while casting. With a bar this size you will get noticeable shrink as it cures (About 1/8 inch over the 16 inch length) and this makes it easy to lift out the block. If it gets stuck, just unscrew the side. I seal my seams with duct tape or painters tape to prevent any resin from leaking out. A 16 inch long by 2 1/2 wide by 1 inch deep mold holds 16 tubes if you space them an inch apart and takes about 19 ounces of resin to fill. I just slice the finished castings apart on my bandsaw when I'm done.

You can buy the white HDPE boards at places like Walmart but those are usually 3/8 thick and for putting screws into them I like the 1/2 inch thick commercial ones and would recommend doing that.

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## ripjack13 (Sep 6, 2016)

Whats with the clamps? To keep it flat or so it doesn't get bumped and spill?


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## Schroedc (Sep 6, 2016)

ripjack13 said:


> Whats with the clamps? To keep it flat or so it doesn't get bumped and spill?



All of the above. 19 ounces of resin creates a pretty decent thermal mass as it cures so the longer molds want to arc a bit. That one has been used over a dozen times. I also don't want it to walk off the top of the table saw if I'm not watching it.

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## Schroedc (Sep 6, 2016)

Also- The larger your mass of Resin, the faster it'll harden. I mixed the resin for both molds in the same container but the long bar mold will gel 30-40% faster than the single molds. IT is because of the increased thermal mass of the resin reaction as the catalyst does it's thing. You can actually mix most poly resins with enough catalyst to set them on fire if you wanted to waste the resin.

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## CWS (Sep 6, 2016)

Excellent! Have you ever used Alumilite?


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## Schroedc (Sep 6, 2016)

CWS said:


> Excellent! Have you ever used Alumilite?



No, my understanding is that alumilite requires pressure to cast and I don't own a pressure pot.


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## CWS (Sep 6, 2016)

Thanks for the quick reply. I use alumilite but I have not tried setting on a saw to vibrate the mold. I will try it though. Thanks


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## Schroedc (Sep 6, 2016)

CWS said:


> Thanks for the quick reply. I use alumilite but I have not tried setting on a saw to vibrate the mold. I will try it though. Thanks



Are you using the clear or which one? What castings are you doing? Would love additional info if you'll share.


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## ripjack13 (Sep 6, 2016)

So...where would I look for sylmar at a good price? And how much should I get to start to see if it's something I would enjoy making....


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## Schroedc (Sep 6, 2016)

ripjack13 said:


> So...where would I look for sylmar at a good price? And how much should I get to start to see if it's something I would enjoy making....



I order from US composites. Works out to about 61.00 per so a gallon. They guarantee fresh material. I would maybe start with a quart to see if you want to continue. I buy two gallons at a time.

Reactions: Thank You! 1


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## gman2431 (Sep 6, 2016)

Very cool!


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## ripjack13 (Sep 6, 2016)

Do i need mekp? I notice there's some postings about getting a 2 oz bottle with some purchases.


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## Schroedc (Sep 6, 2016)

ripjack13 said:


> Do i need mekp? I notice there's some postings about getting a 2 oz bottle with some purchases.



MEKP is the catalyst. They give you enough with the can. Some folks order an extra ounce or two in case they run out but you don't absolutely have to.

Reactions: Thank You! 1


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## CWS (Sep 6, 2016)

Schroedc said:


> Are you using the clear or which one? What castings are you doing? Would love additional info if you'll share.


I use the clear Alumilite. Most of my casting is what they call worthless wood. I will get some pictures. The Alumilite website has some good video on using Alumilite. I don't have any secrets but I learn something everyday. They have a new clear that has open time. I think it has an open time of 12 minutes instead of 7. It may work with the vibration instead of a pressure pot. I use a Harbor Freight paint pot and set it at 70 pounds.


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## barry richardson (Sep 6, 2016)

Man you got some pretty cool uncirculated stamps there!

Reactions: Thank You! 1 | Agree 1


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## Schroedc (Sep 6, 2016)

barry richardson said:


> Man you got some pretty cool uncirculated stamps there!



That's just the tip of the iceberg. I've got about 40 different full sheets to work from. Military, wildlife, states, all kind of things.

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## Schroedc (Oct 18, 2016)

Folks, I'm going to pass along something that just came up with a couple blanks someone sent me to cast, when you paint your tubes white Here are a couple things to keep in mind-

1- Use good quality spray paint. I prefer Rustoleum, what can happen with some paints is something called a recoat lift. When the resin hits the paint it softens it up a lot and causes it to lift off the tube and get wrinkly.

2- Make sure you build several (I do at least 3) coats so you have a good thick base, then knock back any gloss before gluing on the stamps or whatever you are going to cast. LET DRY A WEEK. I know it says 24 hours before use on the can but solvents can be outgassing for a week or more, I like to let them sit a week before knocking back the gloss and gluing to them

3- When prepping the tubes, Make sure they are degreased (I use acetone. lacquer thinner works, even alcohol) and sand them to remove any shine and oxidization and then clean them again with solvent and let dry before painting.

If possible, I find ordering the pre painted tubes from places like PSI and Woodturningz is a good way to minimize this hazard. They are most likely either powder coated or painted with a heat cured, catalyzed automotive style paint that is much more resistant to these kinds of things (I've run close to 100 of them and had absolutely no issues with the paint lifting)

Here is a picture of what can happen-

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## gman2431 (Oct 18, 2016)

Seems like powdercoating them would be an easy route to go?


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## Schroedc (Oct 18, 2016)

gman2431 said:


> Seems like powdercoating them would be an easy route to go?



It's probably the preferred method but unless a guy was going to do a ton of them it could get cost prohibitive unless you already have all the equipment.


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## gman2431 (Oct 18, 2016)

Schroedc said:


> It's probably the preferred method but unless a guy was going to do a ton of them it could get cost prohibitive unless you already have all the equipment.



I powdercoat 1000s of jigs a year with very very minimal equipment.

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## Schroedc (Oct 18, 2016)

gman2431 said:


> I powdercoat 1000s of jigs a year with very very minimal equipment.



Willing to do a tutorial and share some sources? I can see lots of applications in casting and other things we do......


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## gman2431 (Oct 18, 2016)

Schroedc said:


> Willing to do a tutorial and share some sources? I can see lots of applications in casting and other things we do......



Not a problem at all. I've got a couple different ways I do it that most people will already have the basic stuff needed.

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## rocky1 (Oct 18, 2016)

Any idea what happened to this batch? Somebody else paint them? You run out of Rustoleum?


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## Schroedc (Oct 18, 2016)

rocky1 said:


> Any idea what happened to this batch? Somebody else paint them? You run out of Rustoleum?



These were painted by someone else and came to me ready to cast, I did some test runs with the stickers/decals on them on other substrates to make sure those were fine, then went to cast them and had the issue. I'll get some more of the stickers plus the extras that were sent and do up some new ones with the powder coated tubes for the customer.

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## ripjack13 (Oct 18, 2016)

Schroedc said:


> These were painted by someone else and came to me ready to cast,



I bet that moron just used whatever was in his paint bin and the cheapest crap available, because he used it to paint dinosaur footprints in the backyard grass for his grandson, so cheaper the better...
And it was probably this stuff from Walmart's bottom shelf...

Reactions: Funny 4


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## Schroedc (Oct 18, 2016)

ripjack13 said:


> I bet that moron just used whatever was in his paint bin and the cheapest crap available, because he used it to paint dinosaur footprints in the backyard grass for his grandson, so cheaper the better...
> And it was probably this stuff from Walmart's bottom shelf...
> View attachment 115319



Probably, I'm not going to tell anyone who it was though.

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## ripjack13 (Oct 18, 2016)

Right on. 
I'll look around and see if I can find out the dorks id.


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## ripjack13 (Oct 18, 2016)



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## Don Ratcliff (Oct 18, 2016)

Who ever did that should be tar and feathered...

Reactions: Great Post 1 | Funny 1


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## rocky1 (Oct 18, 2016)

Now that was funny!

Reactions: Agree 1 | Funny 1


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## Don Ratcliff (Oct 19, 2016)

ripjack13 said:


> I bet that moron just used whatever was in his paint bin and the cheapest crap available, because he used it to paint dinosaur footprints in the backyard grass for his grandson, so cheaper the better...
> And it was probably this stuff from Walmart's bottom shelf...
> View attachment 115319



My Spanish is a little rusty but I think #4 says "the crap fails fast" but what ever MULEheaded dork used this stuff should probably send some of the stash on his 2 shelves to me. If I were talking to @Schroedc I would say send some to him but I'm not so I won't, just send to me...

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## Schroedc (Jul 25, 2018)

Bit of an update, had to do 500 blanks last year and made a change, I'm warming up my resin bit to make it flow better, then adding the catalyst and then pouring, you have to work fast but I'm not vibrating them any longer as the bubbles float out right away with the warm thin resin.

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## Wildthings (Jul 25, 2018)

Colin how are you warming it and how warm


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## rocky1 (Jul 25, 2018)

In Houston... Sit it in the sun in your backyard for an hour! Loosen the cap a little before you do.


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## Schroedc (Jul 25, 2018)

Wildthings said:


> Colin how are you warming it and how warm



I pour the amount in going to use into a mixing cup and set it in a bowl of hot water.

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## Wildthings (Jul 26, 2018)

rocky1 said:


> In Houston... Sit it in the sun in your backyard for an hour! Loosen the cap a little before you do.


20 minutes -- an hour and it will be cooked off! LOL

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## rocky1 (Jul 26, 2018)

When I keep mine in the fridge, I set the can out for about an hour. If it's at shop temps, there's no need; it runs like water.


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## Johnturner (May 6, 2021)

Colin
Where do you get your stamps?
John


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## Gdurfey (May 6, 2021)

@Schroedc , Colin, I just stumbled onto this thanks to John. Wow, this is great.

@Johnturner , John, I have a lot of stamps from dad. Was going to be retirement income until that hobby completely fizzled. Only issue is they are packed until we get moved later this year. Thanks for stumbling onto this, or finding it, or however you came upon it. I am going to have to slow down and go search for this stuff.


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## Schroedc (May 15, 2021)

Johnturner said:


> Colin
> Where do you get your stamps?
> John



Ebay, antique stores, customers, all over.


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## Lou Currier (May 16, 2021)

The stamp collector in me cringes when I see this but they are cool pens and great keepsakes.

Reactions: Agree 2


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