I picked up a set of foam rubber letters in the craft department at Walmart. Haven't tried it yet, but intend to put them on backwards on contact paper then line the pot mold with them. They aren't real thick (1/4"?) but I thought I'd stain the area darker as well. You may want to give this a try, it's cheap at least!
Leigh

Well!!! I have load of ideas besides buying a set of letters which Leigh suggested. That is the easiest method for sure! :)

I use a variety of methods for engraving letters into my tufa. One is by making a silicone mold of letters I carved out of plaster of paris. I print the lettering I want on a plastic page protector (the lettering has to be in mirror image so that it shows up readable later. I pour a slab of POP and let it harden, turn it over and place the ink side down (on the plastic page protector) on to the plaster slab. Hold it in place and rub finger over plastic to get text to release onto the POP. Then I carve out the letters with any sharp blade. Even exacto knives will work in a pinch.
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Then I apply a coating of Murphy's oil soap or a very SHEER coating of vaseline over the plaster and apply the silicone for making the mold.
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The silicone is patted into a 'wetter' tufa mix and weighed down with a bag of soil until it hardens.
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This is the method I used to make this 'Welcome' sign on my faux rock...
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I know that 'sounds' complicated but it is quite simple.

Another method I used was to let the tufa harden for about three hours and then manually carve out the letters. I print out the text in the font I like, and the size I want and have it right there in front of me as I 'freehand' carve. I used this method on this project...
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And then you can make stamps from hard foam insulation (the pink stuff or blue). Just print out your lettering in mirror image onto another plastic page protector and place it on the foam. Rub the back of the plastic again to apply the ink to the foam. Now trim away all the outsides of the letters and the insides of the 'loops' on letters as in "B". Here is an example of the foam stamp I made...
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I hope this doesn't intimidate you with all the information. Like I said I have tried various means of lettering. The ones that have NOT worked I haven't included! lol

I think that is a lovely idea to make a grave stone with the horses name. If your friend uses any of these ideas, you can also take a simple clipart picture and make a stamp or mold from it as well... something horse appropriate would be nice.

Hope her project goes well! ...

Lettering is easy and for WET tufa requires very little in the way of tools or skill.
You can use those spray paint lettering kits or the plastic tracing ones we all used in school.
Now make youself a few sticks with the ends shaped like the most common shapes of the letters.
Lay the letter over the soft tufa and with the sticks (wax or oil the end so it doesn't stick) punch in the shape of the letter into the damp tufa then take a small brush and smooth the edges. You can work the edges for a nice finish.
If you to crisp these up later after the tufa has cured with a dremel and a grinding stone it's no problem.

There are lots of other ways to letter but this is pretty simple and requires no special tools BUT you do have to work rather quickly if you have a lot to say.:)

Ok, this is pretty pale compared to Marly's WONDERFUL lettering, but this was carved into partially cured tufa using a pen knife. I had printed out the lettering (on paper) and layed it over the stepping stone, then basically transfered the design onto the tufa using the pen knife (outlined the letters and made sure they showed up enough to carve). Then I just started carving. From what I remember the 'recipe' I used was 'rich' in sand, but had peat in it as well.

This stone is almost a year old and still looks good. The odd shape comes from the Celtic knot carved on the other side...

Carving this 'stone' was probably one of my most enjoyable projects to date.

So to answer your question, yes, you can carve letters into tufa!

~GardenChicken

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GardenChicken,

Pale my eye!! That looks great! I agree that Marly does some fabulous work. (I wish she lived in Alabama, right next door to me, and Tango88 on my other side. I would be constantly running back and forth between studios/workshops and seeing all that talent first hand.) However, your letters look first rate to me.

I have been wondering how I could get reverse letters for molding. I have even considered making rubber masks and sandblasting the letters. You guys are very creative at finding ways to do these things. Keep up the good work and thanks for sharing the know-how.

jazz

thanks jazz, I guess that'd make us neighbors 'cuz I want to live right next door to those two as well! LOL

Soooo packrat2... what 'cha gonna do??? If you decide to do the gravestone please post pictures if you get the chance.

Thank you all for the great ideas. Sorry, it takes me awhile to get back to the computer.
I'm thinking Garden Chicken's tecnique on the partially cured 'tufa might be the best way to go for a first project. She does want to write more than just the horse's name and dates so trying to do it on wet tufa might be pushing it. Leigh, those foam rubber letters reversed in the bottom of the mold would probably be great if she weren't going to need multiples of some letters.
Marley, your mold making instructions came up when I did a search. I told my neighbor about the talented person who carves letters out of POP and makes her own silicone mold and she started thinking maybe a wooden cross might be OK. Of course this was after also explaining why If she wanted to have rebar sticking out the bottom to stand it in the ground instead of making the stone longer she should coat with epoxy. :-)
For the recipe I'll probably use 1 cement,1 1/2 sand, 1 sifted peat, and 1/2 vermiculite. Right now the size is 1ft x 2ft x 3in. Were're hoping this won't be TOO heavy.
We should probably try a small test batch first to practice carving. Sure wish I had a dremel. Sorry I can't promise pictures :-( That's one reason I don't post about my projects cuz I know how disappointing it is when there aren't any pictures. I did try awhile ago. My son finally brought his digital camera over and I took some pictures...then after several tries he finally brought the right CD over for downloading from the memory card. Afterwards our cpmputer was all messed up and spent 3 weeks at 'puter Dr.'s house....ended up having to order a new mother board... he said it wasn't our sons fault-just a coincedence but I'm not real anxious to let him try again.
It sure is frustrating being computer illiterate.
packrat2

A Dremel with a router attachment and a handful of cheap diamond stones would work terrific on a flat surface like a grave stone.
I used it to 'sign' my woodworking freehand for years.

And there are plenty of no name dremels around now that are very inexpensive.

But a Ryobi carver could do a terrific job on soft Tufa as well. But the only place you will find one is Ebay.
Check the link.
Dremel also makes a carver of this type but I have not seen one.
I have several Ryobis. I bought them for $10 each when Ryobi decided to stop making them.

I plan to try mine on tufa soon.

Here is a link that might be useful: Ryobi detail carver.

packrat2, did you ever get the stone made for your neighbours horse?? How about pictures? Did you get the camera, etc. working?

Hi Garden Chicken,
Sorry I didn't respond sooner. Nope, we haven't made it yet but are getting closer. I found the stone stamps I had seen on the internet at Ben Franklin' but was disappointed with them. They're a bit on the small side and they put a letter on both sides of each stamp with no rhyme or reason making it frustrating to find the next letter you need.
I did get a Dremel though,YIPEE!! Turns out hubby wanted one too. I did a sample piece scratching the letters in while wet then using the dremel after it set. I tried using sticks like tufaenough suggested but I think my mix was a bit dry. I'm going to try one more test batch with some diffent tools and a wetter mix. Then just need to find a time when we both are free.
Still haven't tried pictures again. My son got his camera fixed but we've had more glitches with the computer and don't dare to mess with it again.

WOW! what a gorgeous weekend here in Maine.
Packrat2

Hi Packrat
A Dremel with the flex cable and a few cheap diamond stones making lettering pretty easy.
Use a tool to press the letters into the soft tufa first.
Just inside the lines so to speak of the finished letter
Then use the dremel AFTER the tufa has cured a bit to carve out the details.
By pressing in the letters first you remove much of the material, making using the dremel to shape each letter much easier.

I actually use a flex cable in my drill press to do this using Dremel bits. Works quite well.

TufaEnough,
What is a flex cable?
Hypertufalady

hypertufalady, a flex cable is a long flexible shaft that attaches to the dremel on one end and your bits go in the other end. Look up Dremel online. Billie