diff --git a/ChangeLog b/ChangeLog
index 72f88875..24f570b9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,7 @@
 - set G_LOG_DOMAIN to VIPS so we can use g_warning etc.
 - added VIPS_DEBUG_MSG() macro
 - --vips-wbuffer2 turns on threadpool for im_iterate as well
+- im_vips2tiff() uses vips_sink() instead of threadgroup
 
 16/1/10 started 7.21.2
 - "invalidate" is careful to keep images alive, so invalidate callbacks can do
diff --git a/TODO b/TODO
index b4e9af0a..9369ebd7 100644
--- a/TODO
+++ b/TODO
@@ -3,8 +3,6 @@
 
 - im_prepare_thread() can go? I think it was only used by im_render()
 
-  wtf, im_vips2tiff.c seems to be using it, what's wrong with im_wbuffer()?
-
 - get rid of threadgroup too (deprecate?)
 
 
diff --git a/libvips/format/im_vips2tiff.c b/libvips/format/im_vips2tiff.c
index aa83a7a3..0464f7ff 100644
--- a/libvips/format/im_vips2tiff.c
+++ b/libvips/format/im_vips2tiff.c
@@ -110,6 +110,8 @@
  * 	- gtkdoc
  * 26/2/10
  * 	- option to turn on bigtiff output
+ * 16/4/10
+ * 	- use vips_sink_*() instead of threadgroup and friends
  */
 
 /*
@@ -230,7 +232,6 @@ typedef struct tiff_write {
 	/* Read from im with these.
 	 */
 	REGION *reg;
-	im_threadgroup_t *tg;
 
 	char *bname;			/* Name for base layer */
 	TIFF *tif;			/* Image we write to */
@@ -252,6 +253,8 @@ typedef struct tiff_write {
 	int embed;			/* Embed ICC profile */
 	char *icc_profile;		/* Profile to embed */
 	int bigtiff;			/* True for bigtiff write */
+
+	GMutex *write_lock;		/* Lock TIFF*() calls with this */
 } TiffWrite;
 
 /* Use these from im_tiff2vips().
@@ -570,14 +573,8 @@ free_layer( PyramidLayer *layer )
 
 	/* And close the TIFF file we are writing to.
 	 */
-	if( layer->tbuf ) {
-		im_free( layer->tbuf );
-		layer->tbuf = NULL;
-	}
-	if( layer->tif ) {
-		TIFFClose( layer->tif );
-		layer->tif = NULL;
-	}
+	IM_FREEF( im_free, layer->tbuf );
+	IM_FREEF( TIFFClose, layer->tif );
 }
 
 /* Free an entire pyramid.
@@ -1032,18 +1029,50 @@ new_tile( PyramidLayer *layer, REGION *tile, Rect *area )
 	return( 0 );
 }
 
+/* Write as tiles. This is called by vips_sink_tile() for every tile
+ * generated.
+ */
+static int
+write_tif_tile( REGION *out, void *seq, void *a, void *b )
+{
+	TiffWrite *tw = (TiffWrite *) a;
+
+	g_mutex_lock( tw->write_lock );
+
+	/* Write to TIFF.
+	 */
+	if( save_tile( tw, tw->tif, tw->tbuf, out, &out->valid ) ) {
+		g_mutex_unlock( tw->write_lock );
+		return( -1 );
+	}
+
+	/* Is there a pyramid? Write to that too.
+	 */
+	if( tw->layer && 
+		new_tile( tw->layer, out, &out->valid ) ) {
+		g_mutex_unlock( tw->write_lock );
+		return( -1 );
+	}
+
+	g_mutex_unlock( tw->write_lock );
+
+	return( 0 );
+}
+
 /* Write as tiles.
  */
 static int
-write_tif_tile( TiffWrite *tw )
+write_tif_tilewise( TiffWrite *tw )
 {
 	IMAGE *im = tw->im;
-	Rect area;
-	int x, y;
 
+	g_assert( !tw->tbuf );
 	if( !(tw->tbuf = im_malloc( NULL, TIFFTileSize( tw->tif ) )) ) 
 		return( -1 );
 
+	g_assert( !tw->write_lock );
+	tw->write_lock = g_mutex_new();
+
 	/* Write pyramid too? Only bother if bigger than tile size.
 	 */
 	if( tw->pyramid && 
@@ -1051,41 +1080,15 @@ write_tif_tile( TiffWrite *tw )
 		build_pyramid( tw, NULL, &tw->layer, im->Xsize, im->Ysize ) )
 			return( -1 );
 
-	for( y = 0; y < im->Ysize; y += tw->tileh ) 
-		for( x = 0; x < im->Xsize; x += tw->tilew ) {
-			/* Set up rect we write.
-			 */
-			area.left = x;
-			area.top = y;
-			area.width = IM_MIN( tw->tilew, im->Xsize - x );
-			area.height = IM_MIN( tw->tileh, im->Ysize - y );
-
-			if( im_prepare_thread( tw->tg, tw->reg, &area ) )
-				return( -1 );
-
-			/* Write to TIFF.
-			 */
-			if( save_tile( tw, tw->tif, tw->tbuf, tw->reg, &area ) )
-				return( -1 );
-
-			/* Is there a pyramid? Write to that too.
-			 */
-			if( tw->layer && new_tile( tw->layer, tw->reg, &area ) )
-				return( -1 );
-
-			/* Trigger any eval callbacks on our source image and
-                         * check for errors.
-			 */
-			if( im__handle_eval( im, area.width, area.height ) ||
-				im_threadgroup_iserror( tw->tg ) ) 
-                                return( -1 );
-		}
+	if( vips_sink_tile( im, tw->tilew, tw->tileh,
+		NULL, write_tif_tile, NULL, tw, NULL ) ) 
+		return( -1 );
 
 	return( 0 );
 }
 
 static int
-write_tif_block( REGION *region, Rect *area, void *a, void *b )
+write_tif_block( REGION *region, Rect *area, void *a )
 {
 	TiffWrite *tw = (TiffWrite *) a;
 	IMAGE *im = tw->im;
@@ -1121,14 +1124,14 @@ write_tif_block( REGION *region, Rect *area, void *a, void *b )
 /* Write as scan-lines.
  */
 static int
-write_tif_strip( TiffWrite *tw )
+write_tif_stripwise( TiffWrite *tw )
 {
 	g_assert( !tw->tbuf );
 
 	if( !(tw->tbuf = im_malloc( NULL, TIFFScanlineSize( tw->tif ) )) ) 
 		return( -1 );
 
-	if( im_wbuffer( tw->tg, write_tif_block, tw, NULL ) )
+	if( vips_sink_disc( tw->im, write_tif_block, tw ) )
 		return( -1 );
 
 	return( 0 );
@@ -1162,28 +1165,11 @@ free_tiff_write( TiffWrite *tw )
 	delete_files( tw );
 #endif /*DEBUG*/
 
-	if( tw->tg ) {
-		im_threadgroup_free( tw->tg );
-		tw->tg = NULL;
-	}
-	if( tw->reg ) {
-		im_region_free( tw->reg );
-		tw->reg = NULL;
-	}
-	if( tw->tif ) {
-		TIFFClose( tw->tif );
-		tw->tif = NULL;
-	}
-	if( tw->tbuf ) {
-		im_free( tw->tbuf );
-		tw->tbuf = NULL;
-	}
-	if( tw->layer ) 
-		free_pyramid( tw->layer );
-	if( tw->icc_profile ) {
-		im_free( tw->icc_profile );
-		tw->icc_profile = NULL;
-	}
+	IM_FREEF( TIFFClose, tw->tif );
+	IM_FREEF( im_free, tw->tbuf );
+	IM_FREEF( g_mutex_free, tw->write_lock );
+	IM_FREEF( free_pyramid, tw->layer );
+	IM_FREEF( im_free, tw->icc_profile );
 }
 
 /* Round N down to P boundary. 
@@ -1211,8 +1197,6 @@ make_tiff_write( IMAGE *im, const char *filename )
 	im_filename_split( filename, name, mode );
 	tw->name = im_strdup( im, name );
 	tw->mode = im_strdup( im, mode );
-	tw->tg = NULL;
-	tw->reg = NULL;
 	tw->bname = NULL;
 	tw->tif = NULL;
 	tw->layer = NULL;
@@ -1228,6 +1212,7 @@ make_tiff_write( IMAGE *im, const char *filename )
 	tw->embed = 0;
 	tw->icc_profile = NULL;
 	tw->bigtiff = 0;
+	tw->write_lock = NULL;
 
 	/* Output resolution settings ... default to VIPS-alike.
 	 */
@@ -1434,14 +1419,6 @@ make_tiff_write( IMAGE *im, const char *filename )
 		tw->compression = COMPRESSION_NONE;
 	}
 
-	/* Make region and threadgroup.
-	 */
-	if( !(tw->reg = im_region_create( tw->im )) ||
-		!(tw->tg = im_threadgroup_create( tw->im )) ) {
-		free_tiff_write( tw );
-		return( NULL );
-	}
-
 	/* Sizeof a line of bytes in the TIFF tile.
 	 */
 	if( im->Coding == IM_CODING_LABQ )
@@ -1766,20 +1743,10 @@ im_vips2tiff( IMAGE *in, const char *filename )
 	}
 
 
-	if( tw->tile ) {
-		/* The strip writer uses wbuffer and does start/end for us, we
-		 * have our own loop for tile writing and so we need to call
-		 * ourselves.
-		 */
-		if( im__start_eval( in ) ) {
-			free_tiff_write( tw );
-			return( -1 );
-		}
-		res = write_tif_tile( tw );
-		im__end_eval( in );
-	}
+	if( tw->tile ) 
+		res = write_tif_tilewise( tw );
 	else
-		res = write_tif_strip( tw );
+		res = write_tif_stripwise( tw );
 	if( res ) {
 		free_tiff_write( tw );
 		return( -1 );
diff --git a/libvips/include/vips/threadpool.h b/libvips/include/vips/threadpool.h
index 85b94f06..358596ac 100644
--- a/libvips/include/vips/threadpool.h
+++ b/libvips/include/vips/threadpool.h
@@ -133,6 +133,10 @@ typedef int (*VipsStop)( void *seq, void *a, void *b );
 int vips_sink( VipsImage *im, 
 	VipsStart start, VipsGenerate generate, VipsStop stop,
 	void *a, void *b );
+int vips_sink_tile( VipsImage *im, 
+	int tile_width, int tile_height,
+	VipsStart start, VipsGenerate generate, VipsStop stop,
+	void *a, void *b );
 
 typedef void (*VipsSinkNotify)( VipsImage *im, Rect *rect, void *a );
 int vips_sink_screen( VipsImage *in, VipsImage *out, VipsImage *mask,
diff --git a/libvips/iofuncs/sink.c b/libvips/iofuncs/sink.c
index 36cdab6d..90517c2f 100644
--- a/libvips/iofuncs/sink.c
+++ b/libvips/iofuncs/sink.c
@@ -301,8 +301,10 @@ sink_progress( void *a )
 }
 
 /**
- * vips_sink:
+ * vips_sink_tile:
  * @im: scan over this image
+ * @tile_width: tile width
+ * @tile_height: tile height
  * @start: start sequences with this function
  * @generate: generate pixels with this function
  * @stop: stop sequences with this function
@@ -310,15 +312,23 @@ sink_progress( void *a )
  * @b: user data
  *
  * Loops over an image. @generate is called for every pixel in the image, with
- * the @reg argument being a region of pixels for processing. vips_sink() is
+ * the @reg argument being a region of pixels for processing. 
+ * vips_sink_tile() is
  * used to implement operations like im_avg() which have no image output.
  *
- * See also: im_generate(), im_open().
+ * Each set of
+ * pixels is @tile_width by @tile_height pixels (less at the image edges). 
+ * This is handy for things like
+ * writing a tiled TIFF image, where tiles have to be generated with a certain
+ * size.
+ *
+ * See also: vips_sink(), vips_get_tile_size().
  *
  * Returns: 0 on success, or -1 on error.
  */
 int
-vips_sink( VipsImage *im, 
+vips_sink_tile( VipsImage *im, 
+	int tile_width, int tile_height,
 	VipsStart start, VipsGenerate generate, VipsStop stop,
 	void *a, void *b )
 {
@@ -335,6 +345,11 @@ vips_sink( VipsImage *im,
 	if( sink_init( &sink, im, start, generate, stop, a, b ) )
 		return( -1 );
 
+	if( tile_width > 0 ) {
+		sink.tile_width = tile_width;
+		sink.tile_height = tile_height;
+	}
+
 	if( im__start_eval( sink.t ) ) {
 		sink_free( &sink );
 		return( -1 );
@@ -353,3 +368,31 @@ vips_sink( VipsImage *im,
 
 	return( result );
 }
+
+/**
+ * vips_sink:
+ * @im: scan over this image
+ * @start: start sequences with this function
+ * @generate: generate pixels with this function
+ * @stop: stop sequences with this function
+ * @a: user data
+ * @b: user data
+ *
+ * Loops over an image. @generate is called for every pixel in the image, with
+ * the @reg argument being a region of pixels for processing. vips_sink() is
+ * used to implement operations like im_avg() which have no image output.
+ *
+ * Each set of pixels is sized according to the requirements of the image
+ * pipeline that generated @im.
+ *
+ * See also: im_generate(), im_open().
+ *
+ * Returns: 0 on success, or -1 on error.
+ */
+int
+vips_sink( VipsImage *im, 
+	VipsStart start, VipsGenerate generate, VipsStop stop,
+	void *a, void *b )
+{
+	return( vips_sink_tile( im, -1, -1, start, generate, stop, a, b ) );
+}
diff --git a/libvips/iofuncs/sinkdisc.c b/libvips/iofuncs/sinkdisc.c
index ea1dedd8..1a32b310 100644
--- a/libvips/iofuncs/sinkdisc.c
+++ b/libvips/iofuncs/sinkdisc.c
@@ -516,14 +516,7 @@ vips_sink_disc( VipsImage *im, VipsRegionWrite write_fn, void *a )
 
 	write_init( &write, im, write_fn, a );
 
-	printf( "initing thread state\n" );
-
-	vips_thread_state_get_type();
-
-	printf( "made thread state\n" );
-
 	result = 0;
-
 	if( !write.buf || 
 		!write.buf_back || 
 		wbuffer_position( write.buf, 0, write.nlines ) ||