diff --git a/src/main/java/org/opencadc/tap/impl/RubinFormatFactory.java b/src/main/java/org/opencadc/tap/impl/RubinFormatFactory.java
new file mode 100644
index 0000000..630a2ac
--- /dev/null
+++ b/src/main/java/org/opencadc/tap/impl/RubinFormatFactory.java
@@ -0,0 +1,34 @@
+package org.opencadc.tap.impl;
+
+import ca.nrc.cadc.dali.util.Format;
+import ca.nrc.cadc.tap.TapSelectItem;
+import ca.nrc.cadc.tap.writer.format.OracleFormatFactory;
+import org.apache.log4j.Logger;
+
+import org.opencadc.tap.impl.RubinURLFormat;
+
+
+public class RubinFormatFactory extends OracleFormatFactory {
+
+    private static Logger log = Logger.getLogger(RubinFormatFactory.class);
+
+    public RubinFormatFactory() {
+    	super();
+    }
+
+    @Override
+    public Format<Object> getClobFormat(TapSelectItem columnDesc) {
+        // function with CLOB argument
+        if (columnDesc != null) {
+            // ivoa.ObsCore
+            if ("ivoa.ObsCore".equalsIgnoreCase(columnDesc.tableName)) {
+                if ("access_url".equalsIgnoreCase(columnDesc.getColumnName())) {
+	            log.info("getClobFormat called for access_url");
+                    return new RubinURLFormat();
+                }
+            }
+        }
+
+        return super.getClobFormat(columnDesc);
+    }
+}
diff --git a/src/main/java/org/opencadc/tap/impl/RubinURLFormat.java b/src/main/java/org/opencadc/tap/impl/RubinURLFormat.java
new file mode 100644
index 0000000..0118771
--- /dev/null
+++ b/src/main/java/org/opencadc/tap/impl/RubinURLFormat.java
@@ -0,0 +1,43 @@
+package org.opencadc.tap.impl;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+
+import ca.nrc.cadc.dali.util.Format;
+import org.apache.log4j.Logger;
+
+
+public class RubinURLFormat implements Format<Object> {
+
+    private static Logger log = Logger.getLogger(RubinURLFormat.class);
+
+    private static final String BASE_URL = System.getProperty("base_url");
+
+    public RubinURLFormat() {
+        super();
+    }
+
+    @Override
+    public Object parse(String s) {
+        throw new UnsupportedOperationException("TAP Formats cannot parse strings.");
+    }
+
+    @Override
+    public String format(Object o) {
+        if (o == null) {
+            return "";
+        }
+
+	String s = (String) o;
+
+	try {
+            URL orig = new URL((String) o);
+	    URL base_url = new URL(BASE_URL);
+	    URL rewritten = new URL(orig.getProtocol(), base_url.getHost(), orig.getFile());
+
+	    return rewritten.toExternalForm();
+	} catch (MalformedURLException ex) {
+            throw new RuntimeException("BUG: Failed to rewrite URL: " + s, ex);
+        }
+    }
+}
diff --git a/src/main/resources/PluginFactory.properties b/src/main/resources/PluginFactory.properties
index 0436817..bd7b92d 100644
--- a/src/main/resources/PluginFactory.properties
+++ b/src/main/resources/PluginFactory.properties
@@ -13,7 +13,7 @@ ca.nrc.cadc.tap.MaxRecValidator.impl = org.opencadc.tap.impl.MaxRecValidatorImpl
 
 ca.nrc.cadc.tap.TableWriter = org.opencadc.tap.impl.RubinTableWriter
 
-ca.nrc.cadc.tap.writer.format.FormatFactory = ca.nrc.cadc.tap.writer.format.OracleFormatFactory
+ca.nrc.cadc.tap.writer.format.FormatFactory = org.opencadc.tap.impl.RubinFormatFactory
 ca.nrc.cadc.tap.upload.datatype.DatabaseDataType = ca.nrc.cadc.tap.upload.datatype.OracleDataType
 
 # the package name here could be changed now that we have a config file