looking for tips on making masters for sand castings

[James Wilson Everett]

Guys,

I get my sand cast parts made at the 18th Century Hardware in Derry Pennsylvania.  They use the patterns I give them without splitting them into two pieces.  Don't ask me how they make the sand molds because I am a bit ignorant, but they do it somehow.  The last castings and molds I actually made myself were back in 8th grade, 1963.

I make the wood patterns from any kind of scrap wood, usually hard maple.  They do end up with a lot of epoxy and JB weld.  I always have several castings made even if I only need one.  This helps when one casting ends up with a major flaw or void, I can scrap it and use another.  Also, the wood original pattern has a short life, so I use a production casting as the pattern if I need additional ones made.  The pattern and castings are thicker & heavier than the anticipated final part so there is a lot of filing to get the finished part.

When I copy a museum original I take the artifact and coat it with a thick layer of 5 minute epoxy.  This takes several applications with some care needed to get a thick layer on the corners and edges.  Then I take it to the 18th Century hardware to have castings made.  The epoxy does two things.  First it gives the casting more thickness to account for the casting shrinkage and for the filing and polishing.  So you end up with a final part that is really close to original dimensions.  The epoxy also protects the artifact surface from damage in the sand casting process.  When finished, the epoxy is removed by submerging the artifact in acetone, leaving the surface and patina intact.  I have done this process with a few original artifact parts from the collection in Fort Ligonier, Pa.

Jim

[David Veith]

A Friend and I have a pour about once a year. Using portro bond  (SP) good detail and can be almost as fine as wax for minor details. Been doing a star patch box that most times we can see the engraving in it. A For  shrinkage factors I have been spray painting them with a dozen coats or so and let dry hard. Lacquer  shellac works good to.
? For  Acer  or Captchee How have you been mounting your half on your board and getting center line to meet at the same point. Thinking of trigger gaurds. Seeing we have been using the whole peice and I want to move from it.
David
 

[Captchee]

I get my sand cast parts made at the 18th Century Hardware in Derry Pennsylvania.  They use the patterns I give them without splitting them into two pieces.  Don't ask me how they make the sand molds because I am a bit ignorant, but they do it somehow.

 i would bet they are making a soft mould from your mould . from there they then can make  numerous  lost  mould   castings and send you back your original  un damaged .

 Its really hard to say because with today’s technologies they can actually scan your  part  or for that mater , any original  item that’s intended to be duplicated. The part is then  cut in 3 dimension in any suitable medium  for their purpose .
 They may in fact be making sand moulds  of your part . Sand moulds are a type of high temp mould  made from sand and  resins . Engine block are actually  still sand cast today  in that very way  .
 Here is a  U  tube  showing that process .

 It all really depend on the company   and the part
 But if they are doing sand casting as they did in the 18th century  they are copying your mould and then cutting it in half  so as to  be able to remove it from a cope and drag OR they are  sand casting with multiple cope and drags . Thus allowing  your original to be removed  from the sand  without damaging  your mould or the sand mould .
 But I would bet that they most likely are making  lost moulds from your original and then  making sand castings from those moulds

[Captchee]

here is a better link showing the casting being made in water

[James Wilson Everett]

Guys,

When I have castings made they are not near the finished shape, just more or less a blank from which I can file/form/bend to the final shape.  Here are some photos of the wood pattern and a casting I had made for a wall gun that is at Old Fort William, Thunder Bay Ontario.  The museum sent to me a big stack of photos to use in making a show-n-tell replica of an original wall gun in their collection.  The wood pattern I modified from an earlier pattern for a British military wall gun, you can see the splice to make it longer.  The castings were made without splitting the wood pattern.  The casting folks use the pattern directly in the sand mold.  This was before stuff was available from the Rifle Shop.







The artifact photos



[i

Here is the same of the triggerguard.  I left the military wood pattern as-is and modified one of the military castings to give the proper shape by adding epoxy.




And the artifact photos





Jim

[Captchee]

For  Acer  or Captchee How have you been mounting your half on your board and getting center line to meet at the same point. Thinking of trigger gaurds. Seeing we have been using the whole peice and I want to move from it.
David

what i do is drill alignment holes  prior to  shaping the mould . that way the  2 halves  fit together  to make one  shape
 those holes are then also drilled through the backer board . so  the 2 halves have no choice but to align when set to the backer board .
 The backer  board also has alignment holes   which match the pins on my  drag . Those pins match the cope . As such everything  aligns  to match each and every time

 yes james , i can see no reason why your moulds could not be cast as one piece . both would simply be laid on their sides . the casting lines show  it ..
 it’s the way your foundry is packing your  sand . It would appear they are doing it from the top . I pack from the bottom. Its more work to do it the way I do it .  But  in doing so I can cast things like the final on your trigger guard , just as you have it after you have shaped it .
 
 i would also point out that for those who think  you cant get fine detail with sand casting , take note that not only did the joint in your butt plate  show up  but  the grain of the wood is also transferred to the casting

[Jim Kibler]

I think it should be said, that it's unlikely that any reputable museum would consider coating parts with epoxy and then stripping with acetone a good practice.  Acetone in particular will remove oil / varnish, patina etc.  Not the best practice in my view.  Now if the parts have little significance or value the situation may be somewhat different.  Also it looks like the butplate casting shown is solid.  That is it isn't hollow.  Am I seeing this correctly, James?  Would certainly make the casting process easier, but quite a departure from historical practice.

Jim

[Captchee]

 I would have to agree that  it would be a rare case where a museum would
a) allow and original part to be  used  in anyway  for a casting
b) allow such a part to be treated in any way  that may  remover historical information .
c) allow that part  out of their immediate care

 Finding such a place that would allow  the above ,  should be IMO considered very lucky .
 Myself , I wouldn’t even ask  for fear of ending up  very quickly on the outside of a locked door .
 Now that being said .  I do know of cases where  museums have aloud Impressions to be made  of original parts . From those  impressions  moulds can be made .  In the two cases where I have personally seen where that was aloud  ,  it was under very strict supervision.
So James , I would  count yourself as very lucky to have been aloud  such leniency  .

 Some years ago Rich sent me  a set of  wood cartouche moulds  that he had made , to see if I could cast them  in their sculpted form .
 I never was able to replicate   the detail despite repeated tries .
 Until that time   my sand castings consisted of  the process which  James has been using .
 One evening while at  the local veterans hall , the topic  of my project came up.
 One of the older vets  suggested that I  visit the local  reserve navy  center  for information .

 There I  met a  Master Chief  by the name of James Radford .
Seems the Navy had a very long history of ship board foundry operations . With complete manuals on the subject  for the ship board  Foundry personnel .
 It took some doing but by going through the US Navy Publications section , I was able to acquire some copies  of basic  material . However as  most military personnel can tell you. Such manuals often have  supplements and attachments .  As such there were large gaps I the information . Added to that , a lot of it had to deal with more modern  applications .
 This lead me  to  trying to find  copies .  One afternoon while  scanning through the Lindsay publication list I came across a listing  that  was titled ;United States Navy , Foundry Manual.
 The description stated it was a 1957 revision of the 1944 manual  containing 291 pages and photos .
 Since  I only tell then had around 150 pages of information  from the Navy , I  jumped on it .

 Its all on sand casting , from  different sands , binders  moulds and mould making to include design . Casting  different alloys and their % of mix , like brass bronze , magnesium , nickel , gun metal ….…….. How to solve and  understand the causes of casting flaws .all the way to building foundries  
 I was surprised at how complete the manual was . It in fact covers a lot of information that I was missing

 While it is only 291 pages , it’s a large 8X11 book with small print . So  tons of information .
 Some of it rather technical . But like all military manuals its written in  very simplified form
 I know there are a lot of foundry books out there .  But that one manual quickly became  the one I go to the most  
 Now understand that this  manual deals with ship board  casting .   So its photos show  the casting of steam valves , gates , fittings pump casings …………However casting all these items are far more complex . Thus the basic information needed for casting basic items like trigger guards , butt plates and side plates  is all easily discernable from the provided information .
 I would highly recommend it  if your thinking about learning to sand cast  or  even if you’re  more  advanced  

[Acer Saccharum]

Dave B told me about florist foam, that green stuff that florists sick in a pot, and shove flower stems into.  it's quite crushable, and takes surprising good detail.

You can squeeze a part in between two blocks of foam, and get a pretty goo mould. Coat mould with elmer's glue, and you can cast a resin part out of the mould, a part which can be built up and used as a foundry pattern.

[Chris Treichel]

If you wanted to go really high tech on copying a historical item.... procedure is to do a three dimensional laser scan and then using a 3 dimensional printer print the stuff out say in plastic (metal printing is possible but very expensive)  you could also adjust the item for shrinkage for a mould.   

[docone]

For investment casting, you can make machineable wax and coat it in slurry.
Take parafin wax, make liquid, then add polyethelene bags into the molten bags.  You might have to cool down the mix to find the mix desired, but, you can make a good model with that.
Rigid, carves nicely, and burns out well.

[whetrock]

Thanks to you all for the tremendous response to my questions. I appreciate all the very helpful photos and links and advice!
whetrock

[Bennypapa]

Way back in college art class we were pouring metal. One of the teachers was not too keen on the rough finish and he used a coating on the master that would give a smoother finish. It looked like thin pancake batter and I assume it was a binder (like shellac or paint) with a filler such as powdered silica or clay. The mold went on after this coating had dried/set.
NOW, this has been years and I didn't get the name of the stuff but a foundry supply place might know what the stuff is.
Just throwing that out there in case it helps anyone out.

[44-henry]

Another option that exists if you want to work from an original without risk of damaging it is to have it 3D scanned. Once a 3D file has been created it can be manipulated to suite your needs. In other words it can be enlarged to allow for shrinkage and split in two. Once completed the file can be printed in ABS plastic on a standard 3D printer. You can also have these cast  from resin that can be used just like wax in an investment process. The resin printers have extremely good resolution if you are looking to capture every bit of detail this is really the way to go.

I have made many casting patterns over the past few years using a 3D printer and they are about ideal for the work that we do. It's not traditional, but it works great. As was mentioned above, with the Petrabond sand that we use (oil bonded) detail can be very good and you can really take advantage of the above process.  Also, there are lots of private companies that cater to those wanting to do this sort of work, just Google and you will find them.